time delay distance
apest-e derang-e zamâni
A distance-like quantity derived from → gravitational lensing time delay. It is given by a combination of three angular diameter distances in a strong lens system: DΔt = (1 + zL)[DA(EL)DA(ES) / DA(LS)], where zL is the → redshift of the → gravitational lens, while DA(EL), DA(ES), and DA(LS) are the angular diameter distances from the Earth to the lens, from the Earth to the source, and from the lens to the source, respectively. As each of the distance is proportional to the inverse of H0, DΔt is proportional to 1/H0.
Fr.: dilatation du temps
A phenomenon related to special and general relativity.
time of periapsis passage
zamân-e gozar az pirâhabâk
Fr.: temps de passage au périapse
Fr.: résolution temporelle
Same → temporal resolution.
Fr.: renversement du temps
A transformation operating on time in the equations of motion of a dynamical system in which t is replaced by -t.
Fr.: échelle de temps
A measure of duration of a specific process, such as → crossing time, → dynamical time scale, → evolutionary time scale, → Kelvin-Helmholtz time scale, → nuclear time scale, → photon escape time, → relaxation time, → star formation time scale.
zonâr-e zamân, zamân-zonâr
Fr.: fuseau horaire
Any of the 24 zones on the Earth surface delimited by → meridians at approximately 15° intervals. In each time zone a common standard time is used, and the time is one hour earlier than the zone immediately to the east.
Fr.: flèche du temps
The sequence of all natural processes in which the → entropy increases. In other words, the fact that these processes all move in one direction in time and are → irreversible. The past is distinctly different from the future; things always grow older, never younger.
Fr.: genre temps
Fr.: intervalle genre temps
Fr.: appareil horaire
Any mechanical, electric, or electronic device, such as a clock or watch, designed to measure and display the passage of time.
Zamân-šomâr, literally "time counter," from zamân, → time, + šomâr "counter," from šomârdan "to count," from Mid.Pers. ôšmârtan, ôšmurtan "to reckon, calculate, enumerate, account for," from Av. base (š)mar- "to have in mind, remember, recall," pati-šmar- "to recall; to long for," hišmar-, cf. Skt. smar- "to remember, become aware," smarati "he remembers," L. memor, memoria, Gk. mermera "care," merimna "anxious thought, sorrow," martyr "witness."
arziz (#), qal'y (#)
A metallic chemical element; symbol Sn (L. stannum for → alloys containing → lead). → Atomic number 50; → atomic weight 118.69; → melting point 231.9681°C; → boiling point 2,270°C; → specific gravity 5.75 (gray), 7.3 (white). The element was known in prehistoric times.
M.E., O.E. tin; cf. M.Du., Du. tin, O.H.G. zin, Ger. Zinn, O.N. tin; related to Fr. étain?
Arziz "tin," from Mid.Pers. arziz "tin, lead,"
arus "white, bright;" Av. ərəzata- "silver,"
auruša- "white;" cf. Skt. arjuna- "white, shining,"
rajata- "silver;" Gk. argos "white," arguron "silver,"
L. argentum "silver," arguere
"to make clear," argmentum "argument;"
PIE *arg- "to shine, be white, bright, clear."
Fr.: bandes TiO
tip of the red giant branch method
raveš-e nok-e šâxe-ye qulhâ-ye sorx
Fr.: méthode du haut de la branche des géantes
A technique for deriving extragalactic distances which uses the → luminosity of the brightest → red giant branch stars in old → stellar populations as a "standard candle." For old (> 2-3 Gyr), metal-poor ([Fe/H] < -0.7) stellar populations, this luminosity is relatively well determined, and the → absolute magnitude of these stars in the I band is roughly constant (MI = -4.1 ± 0.1).
Fr.: miroir inclinable
A rapidly moving → mirror used in → adaptive optics to correct overall movements of the incoming → wavefront of light caused by → atmospheric turbulence. The simplest form of adaptive optics is tip-tilt correction, which corresponds to correction of the tilts of the wavefront in two dimensions. This is done by tipping and tilting the mirror rapidly in response to overall changes in position of a reference star. See also → deformable mirror.
Âyené, → mirror; kaj "turned aside; crooked, bent" (cf. Skt. kubja- "hump-backed, crooked," Pali kujja- "bent," L. gibbus "hump, hunch," Lith. kupra "hump") + -o- "and" + râst→ right + -gar agent noun suffix → -or.
Exhausted of strength and energy.
Past participle of tire "to weary; become weary," M.E. tyren, O.E. teorian, of unknown origin.
Xasté "tired; hurt, wounded;" Mid.Pers. xastan, xad- "to injure, wound;" Av. vīxaδ- "to crush;" Proto-Iranian *xad- "to wound, hurt."
Fr.: fatigue de la lumière
The hypothesis that photons from distant objects lose energy during their intergalactic journey to us, thereby increasing in wavelength and becoming redshifted. This would provide an alternative to the → Big Bang model in accounting for the → redshifts of distant galaxies. However, there is no evidence for any such tired-light effect. First discussed by F. Zwicky (1929, Proceedings of the National Academy of Sciences, 15, 773).
Fr.: paramètre de Tisserand
In celestial mechanics, a combination of orbital elements commonly used to distinguish between comets and asteroids. Objects whose Tisserand's parameter value is smaller than 3 are considered to be dynamically cometary, and those with a value larger than 3 asteroidal. Also called Tisserand's invariant.
Named after François Félix Tisserand (1845-1896), French astronomer, Director of the Paris Observatory (1892).
The largest and the sixth moon of → Saturn discovered by Christiaan Huygens in 1655. Called also Saturn VI. Titan has a diameter of 5,150 km, about half the size of Earth and almost as large as Mars. It orbits Saturn at a mean distance of 1,221,830 km every 15.945 days. It is the only moon known to have an → atmosphere. Its surface temperature is -179 °C, which makes water as hard as rocks and allows → methane to be found in its liquid form. Its surface pressure is slightly higher than Earth's pressure (1.6 bars against 1 bar at sea level). The Huygens probe released from → Cassini-Huygens landed on Titan on December 25, 2004. From the data obtained by Cassini-Huygens, we know that Titan is a world with lakes and seas composed of liquid methane and → ethane near its poles, with vast, arid regions not made of silicates as on Earth, but of solid water ice coated with → hydrocarbons that fall from the atmosphere. Titan's icy dunes are gigantic, reaching, on average, 1 to 2 km wide, hundreds kilometers long and around 100 m high. Titan is the only other place in the solar system known to have an Earth-like cycle of liquids flowing across its surface as the planet cycles through its seasons. Each Titan season lasts about 7.5 Earth years. The Huygens probe made the first direct measurements of Titan's lower atmosphere. Huygens also directly sampled → aerosols in the atmosphere and confirmed that → carbon and → nitrogen are their major constituents. Cassini followed up Huygens' measurements from orbit, detecting other chemicals that include → propylene and poisonous → hydrogen cyanide, in Titan's atmosphere. Cassini's gravity measurements of Titan revealed that this moon is hiding an internal, liquid water and → ammonia ocean beneath its surface. Huygens also measured radio signals during its descent that strongly suggested the presence of an ocean 55 to 80 km below the moon's surface.
In Gk. mythology the Titans were a family of giants, the children of Uranus and Gaia, who sought to rule the heavens but were overthrown and supplanted by the family of Zeus.