Fr.: vitesse d'Alfvén
same as → Alfven speed.
→ Alfven wave; → velocity.
Fr.: vitesse angulaire
A measure of the angular displacement per unit time. Of a particle traveling on a circular path or a rotating body, the ratio of the angle traversed to the amount of time it takes to traverse that angle: ω = dθ/dt. For a rigid body, all lines in it rotate through the same angle in the same time, and the angular velocity is the characteristic of the body as a whole. The angular velocity is related to the linear velocity by the equation v = rω, where r is the distance of the point from the rotation axis. → vector angular velocity.
The departure from → isoplanicity.
→ an-; → isoplanicity.
Fr.: vitesse asymptotique
For → stellar winds, same as → terminal velocity.
→ asymptotic; → velocity.
Fr.: vitesse moyenne
The ratio of the displacement (Δx) of a particle, as it moves from point A to point B, to the corresponding time interval: v = Δx/Δt.
The state of stratification in a fluid in which surfaces of constant pressure do not coincide with those of constant density, but intersect. Where baroclinicity is zero, the fluid is → barotropic. Same as baroclinity.
→ baroclinic; → -ity.
Fr.: vitesse de rupture
The velocity of a → rotating star at which the → centrifugal force equals the → gravitational force. Also known as → critical velocity. The simplest expression of the break-up velocity for an OB star, ignoring the → Eddington luminosity, is given by the relation: v = (GM / R)1/2, where M and R are the mass and radius of the star respectively, and G the → gravitational constant. A more realistic expression takes into account not only the → radiation pressure, but also the non-uniformity of the brightness over the stellar surface, as indicated by → von Zeipel theorem. With these conditions, the break-up velocity has a more complicated formula, corresponding to the velocity reached when somewhere on the star the → total gravity becomes zero.
The ability to receive or contain.
From M.Fr. capacité, from L. capacitatem, from capax "able to hold much," from capere "to take, grasp."
Gonjâyeš "capacity, holding, containing," from gonjdan "to be contained; to hold exactly; to be filled;" Mid.Pers. winj- "to be contained;" Proto-Iranian *uiac-/*uic-; cf. Skt. vyac- "to contain, encompass," vyás- "extent, content, extension;" L. uincire "to bind."
The quality of being physically caustic.
The condition of being → chaotic.
Fr.: ville, cité
Any large town or populous place.
M.E. cite, from O.Fr. cite "town, city," from L. civitas "citizenry; community," from civis "native, townsman;" related to L. cuna "cradle; bed;" Gk. kome "village;" Skt. śiva- "auspicious, dear;" O.E. ham "dwelling, house, village;" E. home; Ger. Heim (→ hamlet); Iranian dialects kiye "house, home;" Xonsâri ki "house;" Anâraki xiya, Tâti Karingân kâ, Sangesari keh "house, home;" PIE *kei- "to lie; bed."
Šahr "city," from Mid.Pers. šahr "land, country, city;" O.Pers. xša- "to rule," pati-xša- "to have lordship over," Xšyāršan- "hero among kings" or "ruling over heroes" the proper name of the Achaemenid emperor Helenized as Xerxes, upari.xšay- "to rule over," xšāyaθiya- "king;" Mid.Pers. šâh "king," pâdixšâ(y) "ruler; powerful; authoritative;" Mod.Pers. šâh "king," pâdšâh "protecting lord, emperor, monarch, king," šâyestan "to be worth, suit, fit;" Av. xšā(y)- "to rule, have power," xšayati "has power, rules," xšāyô "power;" cf. Skt. ksā- "to rule, have power," ksáyati "possesses;" Gk. ktaomai "I acquire," ktema "piece of property;" PIE base *tkeh- "to own, obtain."
compact high-velocity clouds (CHVCs)
abrhâ-ye hampak-e tondrow
Fr.: nuages compacts à grande vitesse
A population of relatively small (typically < 2°) → high-velocity clouds, which are spatially and kinematically isolated from the gas distribution in their environment. They are thought to be located in the → intergalactic medium of the → Local Group.
→ compact; → high-velocity cloud.
Fr.: métallicité critique
The → metallicity of a → star-forming → molecular cloud when → cooling → rates by → metals dominate the → gravitational → heating during → protostellar collapse. The minimum → Jeans mass achieved by gravitational → fragmentation depends on the presence/absence of → coolants in the cloud. Since cooling rate in metal lines is more efficient than in primordial molecular lines (H2 and HD), metals favor fragmentation in gas and formation of → low-mass stars.
→ critical; → metallicity.
Fr.: vitesse critique
1) Velocity of → fluid through a pipe at which the motion
changes from → laminar to
→ turbulent flow.
Fr.: vitesse de dérive
The average velocity of a charged particle in a plasma in response to an applied electric field.
The amount by which the orbit deviates from circularity: e = c/a, where c is the distance from the center to a focus and a the semi-major axis. If e = 0, the orbit is a circle. If e < 1, the orbit is an ellipse, if e > 1 it is a hyperbola, and if e = 1 it is a parabola. The eccentricity is one of the six → orbital elements that define a → Keplerian orbit.
The ability of a body which has been → deformed by an applied → force to return to its original shape when the force is removed. Up to a certain point the material obeys → Hooke's law. See also → ductility, → plasticity.
1) The physical phenomena arising from the behavior of → electrons
and → protons that is caused by the → attraction
of particles with opposite → charges and the
→ repulsion of particles with the same charge.
From L. electrum "amber," from Gk. elektron "amber" + -ity a suffix used to form abstract nouns expressing state or condition.
Barq, Pers. term, used also in Ar. and Hebrew (barak "lightening"); variants in
Pers.: varq, barx, balk, belak, bala;
Lârestâni belak; Tabari, Lahijâni, Semnâni, Sorxeyi, Sangesari belk;
Gilaki val; Lori beleyz; Kurd. bilese;
Tokharian AB pâlk; Mid/Mod.Pers. bir "lightening,"
Mid.Pers. brâh "brilliance, splendour," br'z- "to shine, beam,"
Mod.Pers. barâz "beauty, grace, elegance;"
Av. brāz- "to shine, beam; splendour," brazāiti "shines;" cf.
Skt. bhrāj- "to shine, beam, sparkle," bhrajate "shines;"
Gk. phlegein "to burn;" L. fulgere "to shine," fulmen "lightning,"
flagrare "to blaze, burn;" O.H.G. beraht "bright;" O.E. beorht
"bright;" E. → bright;
PIE base *bherəg-; *bhrēg- "to shine; white."