An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < abs ann con deg exc gen hie int mic ove reg tem > >>

Number of Results: 232 Search : era
temperature gradient
  زینه‌ی ِ دما   
zine-ye damâ (#)

Fr.: gradient de température   

A physical quantity that describes the rate of change of temperature with displacement in a given direction from a given reference point. Same as → thermal gradient.

temperature; → gradient.

temperature inversion
  واگردانی ِ دما   
vâgardâni-ye damâ

Fr.: inversion de température   

Meteo.: A reversal in the normal temperature decrease, the temperature rising with increased elevation in the atmosphere instead of falling. A layer in which temperature increases with altitude.

temperature; → inversion.

tera- (T)
terâ- (#)

Fr.: tera-   

Prefix denoting one million million (1012).

From Gk. teras "monster."

thermodynamic temperature
  دمای ِ گرماتوانیک   
damâ-ye garmâtavânik

Fr.: température thermodynamique   

A temperature scale, measured in → kelvin (K), that is related to the energy possessed by matter; it was formerly known as → absolute temperature. The zero point on the scale (0 K) is absolute zero. Thermodynamic temperature can be converted to temperature on the → Celsius scale by subtracting 273.15.

thermodynamic; → temperature.

Tisserand's parameter
  پارامون ِ تیسران   
pârâmun-e Tisserand

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).

ravâdâri (#)

Fr.: tolérance   

The maximum permissible error or variation in a dimension of an object.

M.E., from O.Fr. tolerance, from L. tolerantia "endurance," from tolerans, pr.p. of tolerare "to bear, endure, tolerate."

Ravâdâri, noun from ravâdâr "consenter; judging right; lawful," from ravâ "admissible; allowable; tolerated" (from raftan "to go, walk; to flow;" Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack" + -dâr "having, possessor" (from dâštan "to have, to possess," Mid.Pers. dâštan, O.Pers./Av. root dar- "to hold, keep back, maitain, keep in mind," Skt. dhr-, dharma- "law," Gk. thronos "elevated seat, throne," L. firmus "firm, stable," Lith. daryti "to make," PIE *dher- "to hold, support").


Fr.: trilatération   

A geometrical method in land surveying for the determination of the relative position of points. In contrast to → triangulation, trilateration involves measuring the lengths of the three sides of touching or overlapping triangles and not their angles.

tri-; → lateral; → side; → -tion.


Fr.: sous-abondance   

The abundance of a chemical element being lower than a reference value, in particular compared to that of the Sun.

under-; → abundance.

unitary operator
  آپارگر ِ یکایی   
âpârgar-e yekâyi

Fr.: opérateur unitaire   

A linear operator whose inverse is its → adjoint. In addition to → Hermitian operators, unitary operators constitute a fundamentally important class of quantum-mechanical operators.

unitary; → operator.


Fr.: parole, déclaration   

1) An act of uttering; a spoken word, statement, or vocal sound.
2) Something uttered; a word or words uttered; a cry, animal's call, or the like.
3) Linguistics: Any speech sequence consisting of one or more words and preceded and followed by silence: it may be coextensive with a sentence (

utter; → -ance.

virial temperature
  دمای ِ ویریال   
damâ-ye viriyâl

Fr.: température du viriel   

The mean temperature at which a gravitationally → bound system would satisfy the → virial theorem. For a system of mass M and radius R with constant density, the gravitational energy per unit mass is W = GM/R. The kinetic energy per unit mass is E = (3/2)kTvir, where k is → Boltzmann's constant and μ the mean molecular weight. According to the virial theorem, E = W/2, which leads to the virial temperature Tvir = (1/3)(GM/kR).

virial; → temperature.

weak interaction
  اندرژیرش ِ نزار، ~ کمزور   
andaržireš-e nezâr, ~ kamzvr

Fr.: interaction faible   

One of the fundamental forces of nature that accounts for some particle interaction, such as → beta decay (→ radioactivity), the decay of free → neutrons, → neutrino interactions, and so forth. It is short-ranged, dominating at distances of 10-16 cm and occurs at a rate slower than that of the → strong interaction by a factor of about 10-13, hence its name. Although the weak interaction also includes interactions in which no neutrinos are emitted, neutrino emission accompanies all weak interactions of interest to astrophysics. Weak interaction plays an important role in the evolution of the stars from birth to death. For example, the → proton-proton reaction is a weak interaction. Also called → weak force or → weak nuclear force.

weak; → interaction.

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