# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 48 Search : principle
 uncertainty principle   پَروَز ِ ناتاشتیگی   parvaz-e nâtâštigiFr.: principe d'incertitude   A quantum mechanical principle due to Werner Heisenberg which states that the position and momentum of a particle cannot be determined simultaneously with any arbitrary accuracy. These quantities can be determined only with accuracies limited by the relation Δx.Δp ≥ (1/2)ħ, where Δx is the error in the determination of the position and Δp is the error in the momentum. A similar relation holds for the energy of a particle and the time, ΔE.Δt ≥ (1/2)ħ. Same as → Heisenberg uncertainty principle.→ uncertainty; → principle. variational principle   پروز ِ ورتشی   parvaz-e vartešiFr.: principe variationnel   Any of the physical principles that indicate in what way the actual motion of a state of a mechanical system differs from all of its kinematically possible motions or states. Variational principles that express this difference for the motion or state of a system in each given instant of time are called → differential. These principles are equally applicable to both → holonomic and → nonholonomic systems. Variational principles that establish the difference between the actual motion of a system during a finite time interval and all of its kinematically possible motions are said to be → integral. Integral variational principles are valid only for holonomic systems. The main differential variational principles are: the → virtual work principle and → d'Alembert's principle.→ variational; → principle. verifiability principle   پروز ِ راست-جُست-پذیری   parvaz-e râst-jost-paziriFr.: principe de vérifiabilité   In logical positivism philosophy, the claim that a statement is literally meaningful (it expresses a proposition) if and only if it either actually has been verified or could at least in principle be verified.Quality noun from → verifiable; → principle. virtual work principle   پروز ِ کار ِ ویر‌آگین   parvaz-e kâr-e virâginFr.: principe du travail virtuel   In → analytical mechanics, a principle whereby it is necessary and sufficient for the equilibrium of any material system with ideal constraints that the sum of the elements of work, performed by the applied forces acting on the system in any virtual displacement, be equal to zero (if all constraints are bilateral) or less than zero (if some of the constraints are unilateral).→ virtual; → work; → principle. weak anthropic principle   پروز ِ انسان-هستی ِ نزار   parvaz-e ensân-hasti-ye nezârFr.: principe anthropique faible   A version of the → anthropic principle whereby the initial conditions in the → Universe are → constrained by the fact that → intelligent life has appeared.→ weak; → anthropic; → principle. weak equivalence principle   پروز ِ هموگ‌ارزی ِ نزار   parvaz-e hamug-arzi-ye nezârFr.: principe d'équivalance faible   All structureless bodies fall along the same → path in a → gravitational field, independent of their composition. Also known as → universality of free fall. See also: → equivalence principle, → Einstein equivalence principle.→ weak; → equivalence; → principle. Weyl's principle   پروز ِ ویل   parvaz-e WeylFr.: principe de Weyl   The → world lines of galaxies form in the 4D space-time a bundle of non-intersecting → geodesics orthogonal to a series of space-like hyperstructures (e.g. Narlikar 2002, An Introduction to Cosmology, 3rd Edition, Cambridge Univ. Press). Expressed differently: The world lines of galaxies, or "fundamental particles," form (on average) a space-time filling family of non-intersecting geodesics converging toward the past (Rugh & Zinkernagel, 2010, astro-ph/1006.5848). The statement is sometimes denoted postulate, assumption, or hypothesis. The importance of Weyl's principle is that it asserts that cosmic matter moves according to certain regularity requirements. See also → cosmological principle.First introduced by the German mathematician Hermann Weyl (1885-1955) in 1923 in his Raum, Zeit, Materie; → principle. work-energy principle   پروَز ِ کار-کاروژ   parvaz-e kâr-kâružFr.: principe travail-énergie   The → work of the resultant force exerted on a particle equals the change in kinetic energy of the particle.→ work; → energy; → principle.

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