The boundary between the → troposphere and → stratosphere. Its height, varying with latitude and seasons, is from 8 km at poles, to 18 km at equator; it is higher during winter time. The atmospheric temperature decreases from ground upward until the tropopause. Then it increases in stratosphere because of the absorption of solar ultraviolet radiation.
→ tropo- + pause "break, cessation, stop," from M.Fr. pause, from L. pausa "a halt, stop, cessation," from Gk. pausis "stopping, ceasing," from pauein "to stop, to cause to cease."
From gašt, → tropo-, + marz "frontier, border, boundary" (Mid.Pers. marz "boundary;" Av. marəza- "border, district," marəz- "to rub, wipe;" Mod.Pers. parmâs "contact, touching" (→ contact), mâl-, mâlidan "to rub;" PIE base *merg- "boundary, border;" cf. L. margo "edge" (Fr. marge "margin"); P.Gmc. *marko; Ger. Mark; E. mark, margin).
The lower part of the Earth's atmosphere in which temperature decreases with height, except for local areas of → temperature inversion.
Fr.: règle de Trouton
The ratio of the → molar heat of vaporization of any liquid to its → boiling point is a constant, about 88 joules per mole per Kelvin. The rule is equivalent to the statement that the → entropy of vaporization is constant. It is not always followed, especially by liquids such as water in which hydrogen bonding occurs between the molecules.
Named after Frederick Thomas Trouton (1863-1922), an Irish physicist; → rule.
Fr.: expérience de Trouton-Noble
An experiment first carried out in 1903 to reveal the absolute motion of the Earth with respect to the → ether. The experiment consists of detecting a torque on a charged parallel-plate → capacitor that was suspended so that its plates were vertical. Since the Earth moves around the Sun, the moving charges were expected to produce magnetic fields, and the resulting torque should tend to turn the capacitor bringing its plates parallel to its velocity. No such effect was observed, and the absence of the torque supports the theory of → special relativity.
Named after Frederick T. Trouton (1863-1922) and Henry R. Noble; → experiment.
A suspension of hostilities for a specified period of time by mutual agreement of the warring parties (Dictionary.com).
M.E. triws, trewes, originally plural of trewe "faith, treaty," from O.E. treow "faith, truth, fidelity; promise," cf. O.Frisian triuwe, M.Du. trouwe, Du. trouw, O.H.G. triuwa, Ger. treue "faith, faithfulness." The Germanic word was borrowed into L.L. as tregua, hence Fr. trève.
Nâpard, literally "not war," from negation prefix nâ-, → un-, + pard, variant of vard in prefixed nabard, âvard "fight, struggle," ultimately from Proto-Ir. *part- "to fight, struggle," cf. Av. pərət- "to fight, struggle."
M.E. trewe (adj. and adv.); O.E. triewe, treowe "trustworthy" (cf. O.Fris. triuwi, Du. getrouw, O.H.G. gatriuwu, Ger. treu, O.N. tryggr, Goth. triggws "faithful, trusty").
Râstin, from râst "right, true; just, upright, straight;" Mid.Pers. râst "true, straight, direct;" Soghdian rəšt "right;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" M.E.; O.E. reht, riht; cf. O.H.G. reht, Ger. recht, O.N. rettr, Goth. raihts; PIE base *reg- "move in a straight line," hence, "to direct, rule."
Fr.: anomalie vraie
One of the standard → orbital elements, which is the angle measured at the → focus nearest the → periapsis of an elliptical orbit, between the periapsis and the → radius vector from the focus to the orbiting body.
true celestial equator
hamugâr-e âsmâni-ye râstin
Fr.: équateur céleste vrai
The → celestial equator of date, which is the → great circle on the → celestial sphere perpendicular to the instantaneous axis of rotation of the Earth. Its interaction with the → ecliptic defines the → vernal equinox of date and the → autumnal equinox of date.
true celestial pole
qotb-e âsmâni-ye râstin
Fr.: pôle céleste vrai
The direction of the Earth's instantaneous rotation pole. It differs from the pole due to the short time-scale (days or decades) variations called → nutation.
Fr.: équateur vrai
Same as → true celestial equator.
Fr.: équinoxe vrai
Fr.: horizon vrai
A large circle of the → celestial sphere whose plane is perpendicular to the radius of the Earth through the point. Same as → astronomical horizon. The → visible horizon usually lies lower than the true horizon. See also → dip of the horizon.
Fr.: nord vrai
The geographic north defined by the rotational pole of the Earth, as opposed to magnetic north defined by the geomagnetic north pole.
Fr.: position vraie
The coordinates of an object for a given date, with respect to the true equator and the true equinoxes for the instant of time in question.
true sidereal time
zamân-e axtari-ye râstin
Fr.: temps sidéral vrai
Fr.: Soleil vrai
Fr.: Trumpler 14
A young → massive star cluster in the → Carina Nebula, lying about 10 arcmin to the north-west of → Trumpler 16. It comprises several → O-type stars. In particular, its core contains at least three very early O-type stars; → HD 93129.
From a catalog by Robert J. Trumpler (1886-1956), the Swiss-American astronomer who studied the → open clusters at Lick Observatory (1930). He was the first to produce a definite evidence of the existence of → interstellar reddening, due to → absorption, and to estimate its magnitude.
Fr.: Trumpler 16
A → massive star, and the most populous cluster of the → Carina Nebula. It contains several → O-type stars and three known → Wolf-Rayet stars in addition to the famous → LBV star → Eta Carinae. Trumpler 16 is probably older than → Trumpler 14.
→ Trumpler 14.
To shorten by cutting off a part.
From L. truncatus "cut off," p.p. of truncare "to maim, cut off," from truncus "mutilated, cut off."
Kol kardan "to cut off the end of; to dock a tail," from kol "docked, short," variants in a large number of dialects: kola, kalta, kel, kelma, koc, kall, kor, kul in Gilaki, Tâleši, Lori, Malâyeri, Hamedâni, Qâeni, and others, cf. Av. kaurvô- "bald, docked," kaurvôduma- "with a bald tail," kaurvôgaoša- "with bald ears;" cf. Gk. kol(os) "docked" (kolouros "dock-tailed;" L. colurus) + kardan "to do, to make" (Mid.Pers. kardan, O.Pers./Av. kar- "to do, make, build," Av. kərənaoiti "makes," cf. Skt. kr- "to do, to make," krnoti "makes," karma "act, deed;" PIE base kwer- "to do, to make").
The act or process of truncating, as → disk truncation.
Verbal noun from → truncate.