Fr.: point Sud
The point on → horizon in direction of → geographic south pole.
Fr.: point de stagnation
A point where the → flow → velocity is → zero. For example a point around an obstacle where a → flow tube splits into two portions.
→ stagnation; → point.
Fr.: point critique, ~ stationnaire
1) Math.: For a → function y =
f(x), a point at which the → tangent
to the graph is
horizontal. In other words, a point where the → slope
is zero: dy/dx = 0.
→ stationary; → point.
Fr.: point subsolaire
The point of the surface of a celestial body (including the Earth) at which the Sun is directly overhead at a particular time.
Fr.: point substellaire
The point on the Earth, or other body, at which a particular star is directly overhead at a given time.
→ substellar; → point.
Fr.: point subterrestre
The point on the surface of a celestial body where the star is perceived to be directly overhead (in zenith). The sublunar point and subsolar point are the equivalent points for the Moon and Sun, respectively.
→ sub-; → terrestrial.
telescope pointing accuracy
rašmandi-ye âmâješ-e durbin, ~ ~ teleskvp
Fr.: précision du pointage de télescope
The accuracy with which a telescope can be pointed to a particular coordinate in the sky.
noqte-ye segâné (#)
Fr.: point triple
The definite pressure and temperature at which all three phases of a substance coexist in → phase equilibrium. The triple point of water has a pressure of 4.58 mm of Hg and a temperature of 273.16 °K.
Noqté, → triple; segâné, from sé→ three + -gâné suffix forming plural entities, from Mid.Pers. -gânag, -gâna.
The closest point in the path of a sound wave to the center of a star, as studied in → asteroseismology. Starting from the surface, the sound wave first moves into the star almost straight toward the center. Its path then deflects, because of the increasing → sound speed, so that it misses the center of the star. After the turning point, the wave moves out again until it reaches the surface, where it is reflected. If exactly an integer number of wavelengths fits between two reflections at the surface, the sound wave corresponds to a → standing wave with a specific pattern of → node lines on the surface.
Fr.: tournant final de la séquence principale
Same as → main-sequence turnoff.
Fr.: point vernal
The intersection point between the → celestial equator and the → ecliptic from where the Sun apparently enters into the northern celestial hemisphere.
Fr.: point X
A configuration of magnetic field lines around a → magnetic null point resembling a cross. See also → O-point.
X, the letter of alphabet whose shape evokes the configuration; → point.
noqte-ye vâdahi, ~ vâdâd
Fr.: limite d'élasticite
The point at which the → strain caused by a → stress on a material begins to increase without further increase in the stress. This point marks the end of → elastic deformation and the beginning of → plastic deformation. Same as → elastic limit.
Fr.: point zéro
1) General: A starting point for making a measurement.
zero point energy
kâruž-e noqte-ye sefr
Fr.: énergie du point zéro, point zéro
The lowest possible energy that a → quantum mechanical system may possess. It is the energy of the → ground state of the system. The term "zero point" refers to the observed fact that → vacuum fluctuations persist at → absolute zero temperature. Same as → vacuum energy.