An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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apsidal precession
  پیشایانِ هباکی   
pišâyân-e habâki

Fr.: précession absidiale   

advance of perihelion, → relativistic precession.

apsidal; → precession.

Arabic astronomy
  اخترشناسی ِ عربی   
axtaršenâsi-ye Arabi (#)

Fr.: astronomie arabe   

The astronomical activities that took place from the 8th to the 14th century in the Middle East, Central Asia, North Africa, and Moorish Spain. Arab/Arabic is not meant as an ethnic but rather a linguistic term. In fact a large number of Non-Arab scholars, mainly Persians, Mongols, and Spanish people, wrote their works in Arabic. Even so, many astronomical works were also produced in the other languages of this civilization, especially Persian and in the later centuries Turkish. For example, the main → zijs were originally written in Persian, a notable example being the Zij of Ulugh Beg (c. A.D. 1394-1449), a landmark in precise observations before the Renaissance. Therefore, the term Arabic astronomy is misleading. It also creates a disparity with respect to Western scholars who wrote in Latin. The term "Latin astronomy" is meaningless and as far as these scholars are concerned, the Latin adjective is not specified. For example, the expressions like "the Latin astronomer Copernicus," "the Latin physicist Newton," or "the Latin philosopher Leibniz" are not used. See also → Islamic astronomy.

M.E. arabik, from O.Fr. arabique, from L. Arabicus; → astronomy.

arbitrary constant
  پایای ِ کامسر   
pâyâ-ye kâmsar

Fr.: constante arbitraire   

A constant quantity in → equations which takes various values but which remains unaffected by the changes in the values of the → variables of the equation. Most → differential equations have more than one → solution. In general, the number of arbitrary constants of an ordinary differential equation is given by the → order of the highest → derivative.

arbitrary; → constant.

arc of separation
  کمان ِ جدایی   
kamân-e jodâyi

Fr.: arc de séparation   

The difference in → right ascension between the → Sun and the → Moon, measured in degrees.

arc; → separation.

arc of vision
  کمان ِ دید   
kamân-e did

Fr.: arc de vision   

The → angular  → difference in → altitude between the → Sun and the → Moon.

arc; → vision.

arc second
  کمان-ثانیه، ثانیه‌ی ِ کمانی   
kamân-sâniyé, sâniye-ye kamâni

Fr.: seconde de degré   

A unit of angular size equal to 1/3.600 of a degree.

arc; → second.

archaeoastronomy
  باستان‌اخترشناسی   
bâstânaxtaršenâsi

Fr.: archéoastronomie   

The study that deals with the astronomical knowledge of prehistoric peoples (season events, calendars, observing sites, astronomical alignments) and its influence on their cultures and societies (mythologies, religions, life). Archaeoastronomy covers the intersection between astronomy and archaeology. Same as → astroarchaeology, megalithic astronomy.

Archeoastronomy, from L. archaeo-, archeo "ancient; earlier; primitive," from Gk. arkhaio-, from arkhaios "ancient" + → astronomy.

Bâstânaxtaršenâsi, from bâstân "ancient" + axtaršenâsi, → astronomy.

argon
  آرگون   
ârgon (#)

Fr.: argon   

A → chemical element which occurs as a colorless, odorless, and tasteless gas in the atmosphere (of which it constitutes 0.94% by volume) and in some volcanic gases; symbol Ar. → Atomic number 18; → atomic weight 39.948; → melting point -189.2°C; → boiling points -185.7°C.

Argon, from Gk. neutral of argos "inactive, idle, lazy," from negation prefix → a- + ergon "work," → energy. It was discovered in 1895 by the Scottish chemist William Ramsay and the English physicist Robert John Strutt (Lord Rayleigh) in liquified atmospheric air.

argument of perihelion
  آروزمان ِ پیراهور   
âruzmân-e pirâhur

Fr.: argument du périhélie   

The angular distance between the → ascending node of an object orbiting the Sun and its perihelion. Argument of perihelion is measured in the → orbital plane with respect to the Sun and in the direction of motion. It is one of the → orbital elements and usually shown with the symbol ω. See also: → argument of perigee, → argument of periapsis.

argument; → perihelion.

argumentation
  آروزش   
âruzeš

Fr.: argumentation   

The presentation and elaboration of an argument or arguments.

Noun from → argument.

arithmetic progression
  فرایازی ِ حسابی   
farâyâzi-yz hesâbi (#)

Fr.: progression arithmétique   

A → sequence of n numbers or quantities such that the difference between any two successive terms is a constant. In particular, if a is the first term, the nth term is a + (n - 1)d, where d is the constant. Also called → arithmetic sequence.

arithmetic; → progression.

Arrhenius equation
  هموگش ِ آرنیوس   
hamugeš-e Arrhenius

Fr.: équation d'Arrhenius   

An important relationship in physical chemistry that combines the concepts of → activation energy and the → Maxwell-Boltzmann distribution law. It is expressed by: k = Ae-Ea/(RT), where k is the chemical → reaction rate, Ea is the activation energy, R is the → gas constant, and T is → temperature.

Named for Svante Arrhenius (1859-1927), Swedish chemist and physicist who suggested the relationship in 1889.

artificial horizon
  افق ِ ساختگی   
ofoq-e sâxtegi

Fr.: horizon artificiel   

A shallow flat vessel filled with → mercury or some other viscous → liquid used in special → sextant for measuring altitudes of celestial bodies at sea in the absence of a → visible horizon.

artificial; → horizon.

ascension
  فرازش   
farâzeš

Fr.: ascension   

The act of ascending; ascent.

Verbal noun of → ascend; → -tion.

assertion
  ستوارش   
sotvâreš

Fr.: affirmation   

The act of asserting or something that is asserted.

assert; → -tion.

assignation
  نشارش   
nešâreš

Fr.: rendez-vous, attribution   

1) An appointment for a meeting.
2) The act of assigning; → assignment (Dictionary.com).

Verbal noun of → assign.

association
  آهزش؛ انجمن   
âhazeš; anjoman (#)

Fr.: association   

1) The act of associating, → associate; the state of being associated.
2) A group of → astronomical objects physically or apparently gathered in a particular area of sky, for example an → stellar association.
3) An organization of persons having a common interest. → dissociation.

Association, noun from → associate.

Âhazeš, verbal noun of → âhazidanassociate. Anjoman, for the meaning 3, from Mid.Pers. anjaman, from Av. han-jamana, from han- "together" + jamana, from gam- "to come;" cf. Skt. samgamana "gathering together."

association member
  هموند ِ آهزش   
hamvand-e âhazeš

Fr.: membre d'une association   

A celestial body making part of an astronomical association.

association; → member.

assumption
  آگرب، فرض   
âgarb, farz (#)

Fr.: supposition   

A fact or statement (as a proposition, axiom, postulate, or notion) taken for granted.

M.E., from L.L. assumption, assumptio "taking up," from L. assumere, → assume.

Âgarb, from â-, nuance prefix, + garb, from Av./O.Pers. grab-, Av. gərəb- "to take, to seize;" cf. Mod.Pers. gereftan "to take; to assume;" Skt. grah-, grabh- "to seize, to take," graha "seizing, holding, perceiving;" M.L.G. grabben "to grab;" E. grab "to take or grasp suddenly;" PIE *ghrebh- "to seize."
Ar. farz "assumption, hypothesis."

asteroid designation
  نامگزینی ِ سیارک   
nâmgozini-ye sayyârak

Fr.: désignation des astéroïdes   

1) For an asteroid whose orbit is precisely known, a number and optionally a proper name, e.g. (7) Iris, (24101) Cassini, (99942) Apophis.
2) For an asteroid whose orbit is not known, a provisional designation composed of four elements: number.letter.letter.(optionally)number. The first number indicates the year of discovery. The first letter denotes the half-month of the discovery (A: first half of January, Y: second half of December; the letter "I" is excluded). The second letter and the following number indicate the order of discovery within the half-month. For example, the first asteroid discovered in the first half of May 1960 is: 1960 JA. Since more than 25 objects (without "I") might be detected within a half-month, the number following the second letter indicates the number of 25 discoveries. Hence, 2001 SD3 was discovered in the second half of September 2001 and was the (D =) 4 + (25 x 3) or the 79th object found during that period.

asteroid; → designation.

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