Fr.: contraction de tenseur
An operation of tensor algebra that is obtained by setting unlike indices equal and summing according to a summation convention.
Fr.: densité de tenseur
A generalization of the tensor concept that like a tensor transforms, except for the appearance of an extra factor, which is the → Jacobian matrix of the transformation of the coordinates, raised to some power, in transformation law. The exponent, which is a positive or negative integer, is called the weight of the tensor density. → weight of a tensor density. Ordinary tensors are tensor densities of weight 0. Tensor density is also called → relative tensor.
Fr.: champ tensoriel
A field of space and time each point of which has multiple directionality, and is describable by a tensor function.
Fr.: perturbation tensorielle
The perturbation in the → primordial Universe plasma caused by → gravitational waves. These waves stretch and squeeze space in orthogonal directions and bring about → quadrupole anisotropy in incoming radiation temperature.
Fr.: rang de tenseur
tensor-vector-scalar (TeVeS) theory
A theory put forward to provide a basis for a relativistic generalization of the → MOdified Newtonian Dynamics (MOND) paradigm. TeVeS is based on three dynamical fields: a tensor field, a vector field, and a scalar field. In contrast to general relativity, it has two metrics, an Einstein metric and a physical metric. TeVeS has attracted considerable attention, since it can explain many galactic and cosmological observations without the need for → dark matter. Proposed by J. D. Bekenstein, 2004, "Relativistic gravitation theory for the modified Newtonian dynamics paradigm", Phys. Rev. D, 70, 083509, arXiv:astro-ph/0403694.
A general term for materials of all types and sizes that are ejected by volcanic eruptions. It includes particles as tiny as volcanic ash and as large as bombs and blocks.
From Gk. tephra "ashes."
Prefix denoting one million million (1012).
From Gk. teras "monster."
A metallic chemical element; symbol Tb. Atomic number 65; atomic weight 158.9254; melting point 1,356°C; boiling point 3,123°C; specific gravity about 8.25. Terbium was discovered by the Swedish surgeon and chemist Carl-Gustav Mosander in 1843 in an yttrium salt, which he resolved into three elements. He called one yttrium, a rose colored salt he called terbium and a deep yellow peroxide he called erbium.
From the "village of Ytterby" in Sweden, where the mineral ytterbite (the source of terbium) was first found.
1) A word or group of words that has a precise meaning and expresses a definite idea,
used in a particular science, art, or profession. See also
→ terminology; → determine.
M.E. terme, from O.Fr., from L. terminus "boundary, limit, end; boundary stone or marker," variant termen "boundary, end;" cognate with Gk. termon "limit, boundary;" Skt. tarman "the top of the sacrificial (usually tripod) post; passage;" Irish tearmann "a refuge, sanctuary, asylum;" this Irish word would point to the sacredness of the sacrificial post in primitive IE customs; Hittite tarma- "peg, plug, nail;" PIE base *ter- "to cross;" cf. Pers. tarm, târem, tarâ-, Av. tar- "to cross over," as below.
Tarm, variant târem "boundary, limit," more specifically "a wooden palisade to exclude people from a garden," also "a wooden building of a circular form with an arched roof" (cf. Irish tearmann, as above), Tabari talm "pole, stick" (that marks a boundary), Tâleši/Tâti talmi "pole, stick," Garkâni taram "lever," Lori, Laki tarm "poles fastened together in order to carry a corpse to the village cemetery;" O.Pers./Av. tar- "to cross over," O.Pers. vi-tar- "to go across," Mid.Pers. vitartan "to pass," Mod.Pers. gozar, gozaštan "to pass, cross;" cf. Skt. tarman "the top of the sacrificial post; passage," tar- "to pass (through), overcome," tárati "crosses, passes," tirás "through, across, beyond;" see also → trans-.
1) pâyâni; 2) pâyâné
1) Forming or found at the extreme point or limit of something,
or relating to the very end of something.
M.E., from L. terminalis "pertaining to a boundary or end, final," from terminus "end, boundary line," → term.
Pâyâni, pâyâné, noun and adj. from pâyân "end, extremity; limit, boundary," from pâ(y) "foot; step" (Mid.Pers. pâd, pây; Av. pad- "foot;" cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; P.Gmc. *fot; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-).
terminal age main sequence (TAMS)
rešte-ye farist bâ senn-e pâyâni
Fr.: séquence principale d'âge terminal
The locus of stars on the → Hertzsprung-Russell diagram that are at the point of exhausting hydrogen in their cores. TAMS forms the upper luminosity boundary of the → main sequence strip. See also → zero age main sequence (ZAMS).
Fr.: vitesse terminale
1) The constant maximum velocity reached by a body falling under gravity through a
liquid or gas, especially the atmosphere. The body ceases
to accelerate downward because the force of gravity is equal
to the opposing force of resistance by the medium.
toš-e pâyâni, šok-e ~
Fr.: choc terminal
The dividing line between the illuminated and the un-illuminated part of the Moon's or a planet's disk.
From L. terminator, from terminare, from terminus→ term.
Šid-marz, literally "light boundary," from šid "light, sunlight" (Mid.Pers. šêt "shining, radiant, bright;" Av. xšaēta- "shining, brilliant, splendid, excellent") + marz "boundary, limit" (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).
1) The system of terms belonging to a particular science, art,
specialized subject, or social group. Terminology is the way of
naming concepts, which generally precede the corresponding terms.
See also → lexicology.
A hybrid word coined first in Fr., before 1764, by Yves Marie André (1675-1764), a Jesuit mathematician and philosopher, from termin, from L. terminus, → term, + epenthetic vowel -o- + Gk. -logia, → -logy. Recoined or borrowed in Ger. Terminologie in 1786, by C.G. Schütz of Jena; first appeared in E. in 1801.
To alter the environment of a planet or moon in a → terraforming process in order to make it habitable for life forms.
The hypothetical process of altering the environment (atmosphere, temperature, surface topography, or ecology) of another planet or moon to improve the chances of survival of an indigenous biology or to allow habitation by terrestrial life forms. See also → ecopoiesis.
Verbal noun of → terraform. The term first appeared in a science fiction novel, Seetee Shock (1949) by Jack Williamson, an American science fiction writer; but the actual concept pre-dates this work.
Pertaining to, consisting of, or representing the Earth as distinct from other planets.
From L. terrestris "earthly," from terra "earth," literally "dry land" (as opposed to "sea"); from PIE base *ters- "to dry" (cf. Pers. tešné "thirsty;" Mid.Pers. tašnak "thirsty;" Av. taršu- "dry," taršna- "thirst;" Skt. trsta- "dry," tars- "to be thirsty;" Gk. teresesthai "to become or be dry," L. torrere "to dry up, roast," Goth. þaursus "dry, barren," O.H.G. derren "to make dry," durst "thirst;" Ger. dürr "arid;" O.E. þurstig "thirsty").
Zamini adj. of zamin, variant zami "earth, floor, land;" Mid.Pers. zamig; Av. zam- "the earth;" cf. Skt. ksam- "the ground, earth;" Gk. khthôn, khamai "on the ground;" L. homo "earthly being" (as in homo sapiens, homicide, humble, humus, exhume), humus "the earth;" O.Russ. zemi "land, earth;" PIE root *dh(e)ghom "earth".
Terrestrial Dynamical Time
zamân-e tavânik-e zamini
Fr.: temps dynamique terrestre
A uniform atomic time scale for apparent geocentric ephemerides defined by a 1979 IAU resolution, which replaced Ephemeris Time. TDT is independent of the variable rotation of the Earth, and the length of the tropical year is defined in days of 86,400 seconds of international atomic time. In 1991 it was replaced by Terrestrial Time.