# 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: 4 Search : Poynting
 Poynting vector   بردار ِ پوینتینگ   bordâr-e PoyntingFr.: vecteur de Poynting   The amount of electromagnetic energy flowing through unit area, perpendicular to the direction of energy propagation, per unit time, given by (c/2 π)[E x H]. → Poynting's theorem. Poynting's theorem   فربین ِ پوینتینگ   farbin-e PoyntingFr.: théorème de Poynting   The space through which electromagnetic radiation passes is filled with electric and magnetic fields at right angles to each other and to the direction of propagation of the radiation. The rate of energy transfer is given by the Poynting vector.In honor of John Henry Poynting (1852-1914), English physicist; → theorem. Poynting-Robertson drag   کره‌ی ِ پوینتینگ-رابرتسون   kerre-ye Poynting-RobertsonFr.: traînée de Poynting-Robertson   A loss of → orbital angular momentum by tiny ring particles associated with their absorption and re-emission of → solar radiation. Also known as the → Poynting-Robertson effect (Ellis et al., 2007, Planetary Ring Systems, Springer). Poynting-Robertson effect   ا ُسکر ِ پوینتینگ-رابرتسون   oskar-e Poynting-RobertsonFr.: effet Poynting-Robertson   The effect of → solar radiation on a small (centimeter-sized) particle in → orbit around the Sun that causes it to lose velocity and fall gradually into the Sun. The particle → absorbs solar radiation and → radiates the energy → isotropically in its own frame. The particle thereby preferentially radiates (and loses → angular momentum) in the forward direction in the → inertial frame of the Sun (aberration effect). This leads to a decrease in the particle's angular momentum and causes it to spiral sunward. In contrast, the → Yarkovsky effect is anisotropic; the object may be accelerated or decelerated.→ Poynting's theorem; Howard Percy Robertson (1903-1961), American physicist and mathematician; → effect.