velocity of light
tondi-ye nur, tondâ-ye ~
Fr.: vitesse de la lumière
A → physical constant which represents the ultimate speed limit for anything moving through space, according to the theory of → special relativity. It is the speed of propagation of → electromagnetic waves in a vacuum, equal to 299,792.458 km/s (nearly 3 x 108 m/s). The velocity of light appears as the connecting link between mass and energy in the → mass-energy relation. Usually denoted by c, from L. celeritas "swiftness," from celer "swift," → acceleration.
Fr.: pression dynamique
Fr.: profil de vitesse
A plot of the fluid velocity as a function of position.
fazâ-ye tondâyi, ~ tondâhâ
Fr.: espace de vitesses
Of a dynamical system, a three-dimensional space which consists of the set of values that the velocity can take (vx, vy, vz). → phase space.
Fr.: relation vitesse-distance
The linear relation wherein all galaxies are moving away from one another, with velocities that are greater with increasing distance of the galaxy. Same as → Hubble's law.
Fr.: vitesse de vent
The speed at which the → stellar wind is forced away from the star. Wind velocities of → hot stars are directly measured from → P Cygni profiles, which indicate velocities from several hundred to several thousand km s-1. See also → escape velocity, → terminal velocity, → velocity law, → radiation-driven wind, → CAK model.
ruye-ye tondâ-ye sefr
Fr.: surface de vitesse nulle
In the → restricted three-body problem, a surface which limits the region of space in which a small body can move. In the expression for the → Jacobi integral, the left side value is always positive or nul; hence the particle motion is confined to the region where U ≤ CJ. The surface that limits this region, defined by U = CJ, is called the zero-velocity surface.