# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 absolute acceleration   شتاب ِ اوست   šetâb-e avastFr.: accélération absolue   For a body that moves with respect to a rotating → reference frame, the vector sum of the observed acceleration, the → Coriolis acceleration, and the → centrifugal acceleration. See also the → Coriolis theorem.→ absolute; → acceleration. absolute dating   سن‌یابی ِ اوست   senn-yâbi-ye avastFr.: datation absolue   Any method of measuring the age of an event or object in years. For example, in geology, this method can, unlike → relative dating, give us the age of a rock or fossil in x number of years. The most widely used and accepted method of absolute dating is → radioactive dating. See also: → radiocarbon dating, → radiometric dating.→ absolute; → dating. absolute error   ایرنگ ِ اوست   irang-e avastFr.: erreur absolue   The difference between the measured value of a quantity x0 and its (true) actual value x, given by Δx = x0 - x. See also: → relative error.→ absolute; → error. absolute humidity   نمناکی ِ ا َوَست   namnâki-ye avastFr.: humidité absolue   In a system of moist air, the ratio of the mass of water vapor to the total volume of the system. → humidity.→ absolute; → humidity. absolute luminosity   تابندگی ِ ا َوَست   tâbandegi-ye avastFr.: luminosité absolue   A star's → intrinsic brightness, i.e. the total amount of energy radiated by the star per second. → Luminosity is often expressed in units of watts or erg/sec. The Sun's absolute luminosity is 3.86 × 1033 erg/sec.→ absolute; → luminosity. absolute magnitude   بُرز ِ ا َوَست   borz-e avastFr.: magnitude absolue   1) The → magnitude a star would have if it were at a distance of 10 → parsecs in a void space, without → interstellar absorption. The absolute magnitude is usually deduced from the → visual magnitude, measured through a V filter (→ UBV system), when it is written as MV. If it is defined for another wavelength, it gets another index (U, B, etc). If the radiation on all wavelengths is included, it becomes absolute → bolometric magnitude, Mbol. The Sun has the absolute magnitude + 4.8. Most of the stars have absolute magnitudes ranging between -9 (→ supergiants) and + 19 (→ red dwarfs) (M.S.: SDE). 2) The brightness a → comet or → asteroid would have if it were at a distance of 1 → astronomical unit both from the Sun and the Earth and were completely illuminated by the Sun (M.S.: SDE).→ absolute; → magnitude. absolute measurement   اندازه‌گیری ِ اوست   andâzegiri-ye avastFr.: mesure absolue   A measurement in which the comparison is directly with quantities whose units are basic units of the system. For example, the measurement of speed by measurements of distance and time is an absolute measurement, but the measurement of speed by a speedometer is not an absolute measurement. Note that the word absolute measurement implies nothing about → precision or → accuracy (IEEE Standard Dictionary of Electrical and Electronics Terms).→ absolute; → measurement. absolute permeability   تراوایی ِ اوست   tarâvâyi-ye avastFr.: perméabilité absolue   → absolute; → permeability. absolute space   فضای ِ اوست   fazâ-ye avastFr.: espace absolu   A fixed space in which physical phenomena occur and whose properties do not depend on what occupies it, nor on the observer. It is a distinguished frame of reference that could show bodies to be truly moving or truly at rest. Absolute space is one of the basic assumptions of → Newtonian mechanics, but it was abandoned in Einstein's → special relativity. See also → absolute time; → space-time.→ absolute; → space. absolute temperature   دما‌ی ا َوَست   damâ-ye avastFr.: température absolue   Also called → thermodynamic temperature, the value of a → temperature in the → Kelvin scale. It is is equal to the temperature on the → Celsius scale -273.15 °C.→ absolute; → temperature. absolute tensor   تانسور ِ اوست   tânsor-e avastFr.: tenseur absolu   A → tensor of → weight  → zero.→ absolute; → tensor. absolute time   زمان ِ اوست   zamân-e avastFr.: temps absolu   A universal time supposed to be the same for all observers at any place in the Universe. Absolute time is one of the foundations of → Newtonian mechanics, but it fails to account for physical phenomena in → reference frames with relative motion. Its abandoning was one of the starting points of → special relativity. See also → absolute space; → space-time.→ absolute; → time. absolute value   ارزش ِ اوست   arzeš-e avastFr.: valeur absolue   For any → real number a, the non-negative value of a without regard to its sign; denoted by |a|. Same as → modulus. The absolute value of a is always either → positive or → zero, but never negative. The absolute value of a number may be thought of as its → distance from zero. The following rules hold: |ab| = |a||b| |a + b|  ≤  |a| + |b| |a - b|  ≥  |a| - |b| For a> 0, |x|  ≤  a if and only if -a  ≤  x  ≤  a.→ absolute; → value. absolute viscosity   وشکسانی ِ اوست   vošksâni-ye avastFr.: viscosité absolue   Same as → viscosity and → dynamic viscosity.→ absolute; → viscosity. absolute zero   صفر ِ ا َوَست   sefr-e avastFr.: zéro absolu   The → zero point of the → Kelvin scale of → temperature; the theoretical point at which all molecular activity ceases, -273.16 °C.→ absolute; → zero. absorb   درشمیدن   daršamidanFr.: absorber   1) General: To suck up or take up. 2) Physics: To retain → energy (radiation or sound, for example) or → matter wholly, without → reflection or → transmission.M.Fr. absorber, from L. absorbere "to swallow up," from ab- "from" + sorbere "suck in;" PIE root *srebh- "to suck, absorb;" cf. Arm. arbi "I drank;" Gk. rhophein "to sup up, gulp down;" Lith. srebiu "to drink greedily;" Proto-Iranian *hrab- "to sip, suck (in)," cf. Pashto raw-, Shaghni râv-, Sariqoli rov-, Ishkashimi ruv- "to suck" (Cheung 2007), Pers. (prefixed) zâlu "leech."Daršamidan, from daršam, from dar- "in, into" + šam, variant of šâm, as in âšâm, âšâmidan "to drink, to sip;" Av. šam- "to drink, sip, swallow;" Skt. cam, camati "to sip, drink, lick up, absorb." absorbable   درشمیدنی   daršamidaniFr.: absorbable   Capable of being absorbed.Absorbable, adj. from → absorb + → -able.Daršamidani adj. from aršamidan "to absorb" + -i, → -able. absorbance   درشمندگی   daršamandegiFr.: absorbance   The ability of a solution or a layer of a substance to absorb → radiation, i.e. the ratio of the intensity of the light incident on the solution to the intensity transmitted by it, in logarithmic scale.→ absorb; → -ance. absorbent   درشمنده   daršamandéFr.: absorbant   1) Any material or → substance that → absorbs. 2) Relating to or capable of → absorption.Absorbent, from → absorb + -ent.Daršamandé from aršam present stem of daršamidan, → absorb, + -andé suffix forming adj. and/or agent name. absorber   درشمگر   daršamgarFr.: absorbeur   Any medium that absorbs something.→ absorb; → -er.