An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 304 Search : act
diffraction pattern
  الگوی ِ پراش   
olgu-ye parâš (#)

Fr.: tache de diffraction   

A series of concentric rings of dark and light color produced by interference.

diffraction; → pattern.

Olgu, loanword from Turkish; parâšdiffraction.

diffraction spike
  سیخک ِ پراش   
sixak-e parâš

Fr.: aigrette de diffraction   

One of several light rays emanating from a bright light source in images taken with → reflecting telescopes. They are artifacts caused by light diffracting around the support or → spider vanes of the → secondary mirror.

diffraction; → spike.

diffraction-limited
  کران‌مند به پراش   
karânmand bé parâš

Fr.: limité par la diffraction   

The quality of an → optical system that is capable of producing images with angular resolution as small as the theoretical limit of the → Airy disk.

diffraction; limited, adj. of → limit.

Karânmand "bounded, limited," from karânboundary + -mand possession suffix; parâš diffraction.

diffuse galactic light
  نور ِ کهکشانی ِ پخشیده   
nur-e kahkašâni-ye paxšidé

Fr.: lumière galactique diffuse   

A minor component of galactic light resulting from the diffusion of starlight by → interstellar dust near the → galactic plane.

diffuse; → galactic; → light.

dilution factor
  کروند ِ اوتالش   
karvand-e owtâleš

Fr.: facteur de dilution   

The energy density of a radiation field divided by the equilibrium value for the same color temperature.

dilution; → factor.

double refraction
  شکست ِ دوتایی   
šekast-e dotâyi

Fr.: double réfraction   

Formation of two refracted rays of light from a single incident ray; property of certain crystals, notably calcite.

double; → refraction.

doubly refracting crystal
  بلور ِ شکست ِ دوتایی   
bolur-e šakst-e dotâyi

Fr.: cristal à double réfraction   

A → transparent → crystalline substance (such as calcite, quartz, and tourmaline) that is → anisotropic relative to the → speed of light. A ray incident normally on such crystals is broken up into two rays in traversing the crystal, → ordinary ray and → extraordinary ray.

doubly; → refracting; → crystal.

Einstein-Hilbert action
  ژیرش ِ اینشتین-هیلبرت   
žireš-e Einstein-Hilbert

Fr.: action de Einstein-Hilbert   

In → general relativity, the → action that yields → Einstein's field equations. It is expressed by:
SEH = (1/2κ)∫d4x (-g)1/2R + Sm,
where κ ≡ 8πG and Sm is the matter part of the action.

Einstein; → Hilbert space; → action.

electron diffraction
  پراش ِ الکترونی   
parâš-e elekroni (#)

Fr.: diffraction des électrons   

A diffraction phenomenon resulting from the passage of electrons through matter, analogous to the diffraction of visible light. This phenomenon is the main evidence for the existence of waves associated with elementary particles; → de Broglie wavelength.

electron; → diffraction.

electroweak interaction
  اندرژیرش ِ برقانزار   
andaržireš-e barqânezâr

Fr.: interaction électrofaible   

The unified description of two of the four fundamental interactions of nature, → electromagnetism and the → weak interaction which would merge into a single force under conditions of extreme temperature (above 1016 degrees, 102 GeV) prevalent in the early history of the → Universe.

electroweak; → interaction.

epact
  بر افزا   
barafzâ

Fr.: épacte   

1) The time that must be added to the lunar year (12 lunations) to make it coincide with the solar year (about 11 days).
2) The moon's age at the beginning of the calendar year.

From Fr. épacte, from L. epacta, from Gk. epaktos, verbal adj. of epagein "to intercalate, add, bring forward," from epi "on" + ag-, from agein "to bring, to lead;" cf. L. agere "to drive, set in motion," → act.

Barafzâ, from bar- "on, upon, up" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + afzâ, afzudan "to add, increase" (Mid.Pers. abzudan "to increase, grow;" O.Pers. abijav- "to increase, add to, promote," from abi-, aiby- "in addition to; to; against" + root jav- "to press forward;" Av. gav- "to hasten, drive;" Sk. jav- "to press forward, impel quickly, excite," javate "hastens").

exact
  رزین   
razin

Fr.: exact   

1) Strictly accurate or correct; precise, as opposed to approximate.
2) The complete solution of an equation. For example, in the equation x2 = 7, the positive solution 2.646 is correct to three decimal places. The exact answer is x = 71/2.
See also:
exact differential, → exact differential equation, → exact science, → accurate, → precise, → rigorous.

From L. exactus, p.p. of exigere, literally "to drive out, thrust out," also "demand, finish, measure," from → ex- "out" + agere "drive, lead, act," → act.

Razin "firm, solid, strong" [Dehxodâ, Steingass], Mid.Pers. razên "firm, strong, secure, solid."

exact differential
  دگرسانه‌ی ِ رزین   
degarsâne-ye razin

Fr.: différentielle exacte   

If N(x,y) is a → function of two → independent variables, then dN = (∂N/∂x)dx + (∂N/∂y)dy is the exact differential.

exact; → differential.

exact differential equation
  هموگش ِ دگرسانه‌ای ِ رزین   
hamugeš-e degarsâneyi-ye razin

Fr.: équation différentielle exacte   

A → differential equation composed of → continuous  → differentiable functions for which certain conditions are fulfilled. The equation M(x,y)dx + N(x,y)dy = 0 is called exact if M(x,y) and N(x,y) are continuous differentiable functions for which the following relationship is fulfilled: ∂M/∂y = ∂N/∂x, and ∂M/∂y and ∂N/∂x are continuous in some region.

exact; → differential; → equation.

exact number
  عدد ِ رزین   
adad-e razin

Fr.: nombre exact   

A value that is known with complete certainty. Examples of exact numbers are defined numbers, results of counts, certain unit conversions. Some examples: there are exactly 100 centimeters in 1 meter, a full circle is exactly 360°, and the number of students in a class can exactly be 25.

exact; → number.

exact science
  دانش ِ رزین   
dâneš-e razin

Fr.: science exacte   

A field of study that admits especially precise predictions and rigorous methods of testing hypotheses, especially reproducible experiments involving quantifiable predictions and measurements.

exact; → science.

extragalactic
  استرکهکشانی، برون‌کهکشانی   
ostar-kahkašâni, borun-kahkašâni

Fr.: extragalactique   

Of, pertaining to, or dealing with the space beyond the Milky Way.

From → extra- + → galactic.

extragalactic astronomy
  اخترشناسی ِ استرکهکشانی، ~ برون‌کهکشانی   
axtaršenâi-ye ostar-kahkašâni, ~ borun-kahkašâni

Fr.: astronomie extragalactique   

The branch of astronomy that deals with objects beyond the Milky Way, especially galaxies and quasars.

extragalactic; → astronomy.

extragalactic background light (EBL)
  نور ِ پس-زمینه‌ی ِ استر-کهکشانی   
nur-e paszimine-ye ostarkahkeši

Fr.: lumière du fond extragalactique   

The integrated intensity of all of the light emitted throughout the history of the Universe across the whole of the → electromagnetic spectrum, including those which are not individually detected. The EBL spectrum includes cosmological backgrounds associated with either primordial phenomena, such as the → cosmic microwave background radiation (CMBR), or photons emitted by stars, galaxies and → active galactic nuclei (AGN) due to → nucleosynthesis or other → radiative processes, including → dust scattering, → absorption and reradiation. The EBL may also contain signals that are diffuse and extended, including high-energy photons associated with dark matter particle decays or annihilation.

extragalactic; → background; → light.

fact
  باشا، بوده   
bâšâ, budé (#)

Fr.: fait   

Something that has actual existence; a piece of information presented as having objective reality. → scientific fact.

L. factum "event, occurrence," literally "something done, deed," from neut. p.p. of facere "to do" (cf. Fr. faire, Sp. hacer), from PIE base *dhe- "to put, to do" (cf. Mod.Pers. dâdan "to give;" O.Pers./Av. dā- "to give, grant, yield," dadāiti "he gives; puts;" Skt. dadáti "puts, places;" Hitt. dai- "to place;" Gk. tithenai "to put, set, place;" Lith. deti "to put;" Czech diti, Pol. dziac', Rus. det' "to hide," delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do").

Bâšâ, from bâš + agent suffix; bâš, present stem of budan "to be," from Mid.Pers. budan, from O.Pers./Av. bav- "to be; become, take place;" Av. buta- perf. ptcpl. pass., bavaiti "becomes" (cf. Skt. bhavati "becomes, happens," bhavah "becoming; condition, state;" PIE *bheu- "to be, come into being, become;" Gk. phu- "become," phuein "to bring forth, make grow;" L. fui "I was" (perf. tense of esse), futurus "that is to be, future;" Ger. present first and second person sing. bin, bist; E. to be; Lith. bu'ti "to be;" Rus. byt' "to be"); budé also from budan.

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