# 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: 24 Search : factor
 Lorentz factor   کروند ِ لورنتز   karvand-e LorentzFr.: facteur de Lorentz   In → special relativity, an important parameter which appears in several equations, including → time dilation, → length contraction, and → relativistic mass. It is defined as γ = 1 / [1 - (v/c)2]1/2 = dt/dτ, where v is the velocity as observed in the reference frame where time t is measured, τ is the proper time, and c the → velocity of light. Same as Lorentz γ factor.→ Lorentz; → factor. reflection factor   کروند ِ بازتاب   karvand-e bâztâbFr.: facteur de réflexion   The ratio of total flux that is reflected from a surface to the incident flux. Also called reflectance, reflectivity.→ reflection; → factor. scale factor   کروند ِ مرپل   karvand-e marpelFr.: facteur d'échelle   Math.: A number which scales, or multiplies, some quantity. In the equation y = Cx, C is the scale factor for x. C is also the coefficient of x, and may be called the constant of proportionality of y to x. Geometry: The ratio of any two corresponding lengths in two similar geometric figures. The ratio of areas of two similar figures is the square of the scale factor.→ scale; → factor. Stokes friction factor   کروند ِ مالش ِ استوکس   karvand-e mâleš-e StokesFr.: facteur de friction de Stokes   For the translational motion of a spherical body moving in a → viscous fluid, the proportionality factor between the uniform flow velocity far from the sphere and the drag force, provided no-slip boundary condition and small → Reynolds numbers: f = 6πηR, where η is the Reynolds number and R radius of the sphere.→ Stokes; → friction; → factor.

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