# 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: 10 Search : path
 directed path   په ِ سودار   pah-e sudârFr.: chemin orienté   In a → directed graph, a path in which all → edges are oriented in the same direction.→ directed; → edge. LISA Pathfinder   رهیاب لایزا   rahyâb LISAFr.: LISA Pathfinde   An → ESA spacecraft that was launched on December 3, 2015 to test technologies needed for the Evolved Laser Interferometer Space Antenna (eLISA), an ESA → gravitational wave observatory planned to be launched in 2034. LISA Pathfinder paves the way for future missions by testing in flight the very concept of gravitational wave detection.LISA, short for → Laser Interferometer Space Antenna; → pathfinder. mean free path   پویش ِ آزاد ِ میانگین   puyeš-e âzâd-e miyângin (#)Fr.: libre parcours moyen   The mean distance which a particle moves between two successive collisions with other particles of the medium. Mean free path is inversely proportional to the number of particles per cm3 (n), and the collision → cross section (σ). In the case of a gas with molecules having a diameter of d, the cross section is equal to the area of a circle of radius d, i.e. σ = πd2, and the mean free path is given by: l = 1/(nσ). Taking into account the relative velocity distribution of the colliding molecules, l = 1/(√2 . nσ). For a gas at one atmosphere pressure and room temperature, the average distance between molecules is roughly 3.5 × 10-7 cm, that is some 35 times the diameter of a molecule. Taking the gas density n = 2.4 × 1014 molecules cm-3, and a typical diameter d = 2 × 10-8 cm for a molecule, the mean free path is 3.3 × 10-5 cm. This means that the average distance between collisions is about 95 times the average distance between molecules.→ mean; → free; → path.Puyeš, verbal noun of puyidan "to run, trot; wander," from Mid.Pers. pôy-, pwd- "to run;" cf. Gk. speudein "to hasten;" Lith. spudinti; âzâd, → free; miyângin, → mean. optical path   راهِ نوری   râh-e nuri (#)Fr.: chemin optique   In → geometric optics, the distance a light ray would travel in a vacuum in the same time it travels from one point to another, a specified distance, through one or more optical media.→ optical; → path. path   په، راه   pah, râhFr.: chemin, trajectoire; bande   1) A route, course, or track along which something moves. 2) A course of action, conduct, or procedure. 3) Math.: A continuous curve that connects two or more points. 4) In → graph theory, a → graph whose → vertices can be arranged in a sequence.O.E. paÃ¾, pÃ¦Ã¾; cf. O.Fris. path; M.Du. pat; Du. pad; O.H.G. pfad; Ger. Pfad "path."Pah "path, way," from O.Pers. paθi- "path, way;" Av. paθ-, variants paθi-, paθā-, pantay- (with conversion of -θ- to -h-, as in ciθra-/cehr, xšaθra-/šahr/šâh, vərəθraγna-/bahrâm, → Mars); Mid/Mod.Pers. pand "path, advice, counsel;" Khotanese pande "road, path;" Ossetic fœndœg "path, road;" cf. Skt. pánthā- "road, path, course;" Gk. patos "path, way," pontos "sea;" L. pons "bridge, path;" P.Gmc. *finthanan "to find;" E. find; PIE base *pent- "to go, to tread." Râh, → way. path line   خط ِ په   xatt-e pahFr.: trajectoire particulaire   The path followed by an individual particle of fluid over an interval of time. It contrasts with the → streamline that represents an instantaneous picture of the motion of particles.→ path; → line. path of totality   په ِ هماکی   pah-e hamâkiFr.: bande de totalité   The path (up to 320 km wide) that the Moon's shadow traces on the Earth during a total solar eclipse.→ path; → totality. pathfinder   رهیاب   rahyÃ¢b (#)Fr.: Ã©claireur   1) A person who makes or finds a way, especially through unexplored areas or fields of knowledge. 2) An airplane, or a person dropped from a plane, sent into a target area to illuminate the area for succeeding aircraft (Dictionary.com). 3) → LISA pathfinder.→ path; → finder. thermodynamic path   په ِ گرماتوانیک   pah-e garmâtavânikFr.: chemin thermodynamique   The loci of various changes between two → states through which a → thermodynamic system passes during a → thermodynamic process.→ thermodynamic; → path. totality path   په ِ هماکی، گذرگاه ِ ~   pah-e hamâki, gozargâh-e ~Fr.: ligne de totalité   Of a → solar eclipse, the path of the → umbra across the → Earth. The totality path is usually about 100 km across, but under the most favorable conditions, when the → Moon is at its nearest → distance to Earth and the Earth is at its farthest distance from the Sun, the umbra can have a diameter of about 270 km.→ totality; → path.