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: 554
third contact
  پرماس ِ سوم   
parmâs-e sevom

Fr.: troisième contact   

The end of the total phase of a solar eclipse marked by the trailing edge of the Moon first revealing the Sun.

third; → contact.

third dredge-up
  برونکشید ِ سوم   
borunkešid-e sevom

Fr.: troisième dragage   

A → dredge-up process that occurs in the stellar interior during He shell burning, as in → asymptotic giant branch (AGB) stars. These stars consist of a degenerate carbon-oxygen core, surrounded by a helium-rich region, above which lies a hydrogen-rich convective envelope. Following thermal pulses of the helium-burning shell, the convective envelope moves inward in mass, penetrating the hydrogen-exhausted regions. This is known as third dredge-up. As convection moves inward, nuclear processed materials are carried to the surface.

third; → dredge-up.

third law of thermodynamics
  قانون ِ سوم ِ گرماتوانیک   
qânun-e sevom-e garmâtavânik

Fr.: troisième loi de la thermodynamique   

The → entropy of an idealized state of maximum order is zero at the temperature of → absolute zero. Another version of this law: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.

third; → law; → thermodynamics.

third quarter
  چارک ِ سوم   
cârak-e sevom

Fr.: troisième quartier   

The phase of the Moon when half the visible disk of the waning Moon is illuminated. This quarter occurs when the celestial longitude of the Moon is 270° greater than the Sun's.

third; → quarter.

thirty
  سی   
si (#)

Fr.: trente   

A cardinal number, 10 times 3.

M.E. thritty, O.E. thritig, from thri, threo "three" + -tig "group of ten, -ty."

Si, from Mid.Pers. sih; O.Pers. *ciθas nominative singular of *ciθant-; Av. θrisant- "thirty;" cf. Skt. trimśát- "thirty."

Tholen classification
  رده‌بندی ِ تولن   
radebandi-ye Tholen

Fr.: classification de Tholen   

A fundamental system for the classification of → asteroids based on → albedo and → spectral characteristics. The Tholen scheme includes 14 types with the majority of asteroids falling into one of three broad categories, and several smaller types. → C-type asteroid, → M-type asteroid, → S-type asteroid.

David J. Tholen (1984) Ph.D. thesis, University of Arizona; → classification.

Thomson
  تامسون   
Thomson

Fr.: Thomson   

The British physicist Sir Joseph John Thomson (1856-1940), discoverer of the electron (1897), Nobel Prize in Physics (1906). → Thomson atom, → Thomson cross section, → Thomson effect, → Thomson scattering, → Joule-Thomson effect.

Thomson atom
  اتم ِ تامسون   
atom-e Thomson (#)

Fr.: atome de Thomson   

The earliest theoretical description of the inner structure of atoms whereby an atom consists of a sphere of positive electricity of uniform density, throughout which is distributed an equal and opposite charge in the form of electrons. The diameter of the sphere was supposed to be of the order of 10-8 cm, the magnitude found for the size of the atom. → Rutherford atom.

Thomson; → atom.

Thomson cross section
  سکنج‌گاه ِ تامسون   
sekanjgâh-e Thomson

Fr.: section efficace de Thomson   

The → cross section involved the → Thomson scattering of electromagnetic waves by a free electron. It is defined by: σT = 8πre2/3, where re is the classical → electron radius. Its value is 0.665 245 x 10-28 m2.

Thomson; → cross; → section.

Thomson effect
  اسکر ِ تامسون   
oskar-e Thomson

Fr.: effet de Thomson   

The absorption or emission of heat when current is passed through a single conductor whose ends are kept at different temperatures. If current is passed from hotter end to colder end of a copper wire, then heat is evolved along the length of the wire. When current is passed from colder end to the hotter end, then heat is absorbed.

Thomson; → effect.

Thomson scattering
  پراکنش ِ تامسون   
parâkaneš-e Thomson (#)

Fr.: diffusion de Thomson   

The classical, → non-relativistic scattering of photons by free charged particles. When an electromagnetic wave is incident on a charged particle, the electric and magnetic components of the wave exert a force on the particle, setting it into motion. As it accelerates, it in turn radiates in all directions. Such scattering is independent of wavelength and equal numbers of photons are scattered forward and backward. Thomson scattering occurs in stellar atmospheres and in any non-relativistic → plasma. Thomson scattering is normally taken as the minimum → opacity.

Thomson; → scattering.

thorium
  توریوم   
toriom (#)

Fr.: thorium   

A soft, ductile, lustrous, silver-white, → radioactive metal; symbol Th. → Atomic number 90; → atomic weight 232.0381; → melting point about 1,750 °C; → boiling point about 4,790 °C; → specific gravity 11.7 at 20 °C. It was discovered in the mineral thorite (ThSiO4) by the Swedish chemist Jons Jacob Berzelius in 1828. It was first isolated by the chemists D. Lely Jr. and L. Hamburger in 1914.

Thorium-232 is a → fertile isotope, naturally occurring, from which the → fissile isotope uranium-233 can be bred.

From Thor, the "Scandinavian god of thunder."

thought
  اندیشه   
andišé (#)

Fr.: pensée, réflexion   

The product of mental activity; that which one thinks; the act or process of thinking.

M.E. thoght; O.E. (ge)thoht, from stem thencan "to think;" cf. O.Fris. thinka, O.S. thenkian, O.H.G. denchen, Ger. denken "to think."

Andišé, noun from andišidan, → think.

thought experiment
  اندیش-آزمایش، آزمایش ِ اندیشه‌ای   
andiš-âzmâyeš, âzmâyeš-e andišeyi

Fr.: expérience de pensée   

A demonstration which is carried out in the realm of the imagination, rather than in a laboratory. Thought experiments are designed to test ideas, theories, and hypotheses which cannot physically be tested, at least with current scientific equipment. Some examples: → Maxwell's demon; → Einstein's elevator; Heisenberg's gamma-ray microscope; → Schrodinger's cat. Also called Gedanken experiment.

thought; → experiment. Based on both the Ger./L. compound Gedankenexperiment and its Ger. equivalent Gedankenversuch.

threat
  هرش   
harš (#)

Fr.: menace   

1) A declaration of an intention or determination to inflict punishment, injury, etc., in retaliation for, or conditionally upon, some action or course; menace.
2) An indication or warning of probable trouble (Dictionary.com).

M.E. threte, O.E. threat "pressure, oppression;" cognate with O.N. thraut "hardship, bitter end," Du. verdreiten, Ger. verdrießen "to vex," L. trudere "to press, thrust."

Harš, from Kurd. haraša "threat," haraša kirdan "threaten," related to Mid/Mod.Pers. rašk "envy, jealousy;" Lori, Laki erešt "assault, attack;" Tabari ârâšt "curse, anathema;" Av. arš- "to be envious;" Skt. īrs- "to be envious, envy;" Arm. her "anger, quarrel;" O.E. eorsian "to be malicious;" Proto-Ir. Harš- "to be envious."

threaten
  هرشیدن   
haršidan

Fr.: menacer   

1) To utter a threat against; menace.
2) To be a menace or source of danger to (Dictionary.com).

From M.E. thretnen, from O.E. thrêatnian, → threat

Infinitive from harš, → threat.

three
  سه   
sé (#)

Fr.: trois   

A cardinal number, 2 plus 1.

M.E.; O.E. threo, thrib, feminin and neuter of thri(e); cf. O.Fris. thre, M.Du., Du. drie, O.H.G. dri, Ger. drei, Dan. tre), cognate with Pers. , as below.

, from Mid.Pers. ; Av. θrayô, θrayas, tisrô, θri; cf. Skt. tráya, tri, trini; Gk. treis, L. tres, Lith. trys, O.C.S. trye, Ir., Welsh tri, O.E. threo, as above; PIE base *trei-.

three-body problem
  پر‌آسه‌ی ِ سه‌جسم   
parâse-ye sé jesm

Fr.: problème à trois corps   

The mathematical problem of studying the positions and velocities of three mutually attracting bodies (such as the Sun, Earth and Moon) and the stability of their motion. This problem is surprisingly difficult to solve, even in the simple case, called → restricted three-body problem, where one of the masses is taken to be negligibly small so that the problem simplifies to finding the behavior of the mass-less body in the combined gravitational field of the other two. See also → two-body problem, → n-body problem.

three; → body; → problem.

three-dimensional flow
  تچان ِ سه-وامونی   
tacân-e sé-vâmuni

Fr.: écoulement tri-dimensionnel   

A flow whose parameters (velocity, pressure, and so on) vary in all three coordinate directions. Considerable simplification in analysis may often be achieved, however, by selecting the coordinate directions so that appreciable variation of the parameters occurs in only two directions, or even only one (B. Massey, Mechanics of Fluids, Taylor & Francis, 2006).

three; → dimensional; → flow.

threshold
  آستانه   
âstâné (#)

Fr.: seuil   

The level that must be reached for a physical effect to begin or be noticeable.

M.E. threschold, O.E. threscold, threscwald "doorsill, point of entering."

Âstâné "threshold; a place of rest or sleeping," variant âstân; Mid.Pers. âstânak; ultimately from Proto-Iranian *ā-stānaka-, from *stā- "to stand;" cf. O.Pers./Av. sta- "to stand, stand still; set;" Av. hištaiti; Mid.Pers. êstâtan "to stand;" Mod.Pers. istâdan "to stand;" cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand."

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