An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1002
physical constant
  پایای ِ فیزیکی   
pâyâ-ye fiziki (#)

Fr.: constante physique   

A fundamental → physical quantity that is generally believed to be both universal in nature and constant in time.

physical; → constant.

physical dimension
  وامون ِ فیزیکی   
vâmun-e fiziki

Fr.: dimension physique   

Any of basic physical quantities, such as mass, length, time, electric charge, and temperature in terms of which all other kinds of quantity can be expressed.

physical; → dimension.

physical law
  قانون ِ فیزیکی   
qânun-e fiziki (#)

Fr.: loi physique   

A theoretical principle which is deduced from particular observational facts regarding the behavior of matter. Physical laws are expressed by a general statement that a particular → physical phenomenon always occurs if certain → conditions are present.

physical; → law.

physical libration
  رخگرد ِ فیزیکی   
roxgard-e fiziki

Fr.: libration physique   

Slight oscillations in the rotation of the Moon caused by the gravitational attraction of the Earth on the equatorial bulge of the Moon. → geometrical libration; → libration.

physical; → libration.

physical optics
  نوریک ِ فیزیکی   
nurik-e fiziki

Fr.: optique physique   

The branch of optics concerned with the wave properties of light, → diffraction, → polarization, and other phenomena for which the ray approximation of → geometric optics is not valid. Also called → wave optics.

physical; → optics.

physical parameter
  پارامون ِ فیزیکی   
pârâmun-e fiziki

Fr.: paramètre physique   

Any of a set of physical properties whose values determine the characteristics or behavior of a system; for example, → mass, → size, → temperature, → luminosity, etc.

physical; → parameter.

physical phenomenon
  پدیده‌ی ِ فیزیکی   
padide-ye fiziki (#)

Fr.: phénomène physique   

A natural → phenomenon that can be explained by → physical laws.

physical; → phenomenon.

physical quantity
  چندی ِ فیزیکی   
candi-ye fiziki (#)

Fr.: quantité physique   

A physical → property that can be measured and/or calculated.

physical; → quantity.

physical system
  راژمان ِ فیزیکی   
râžmân-e fiziki

Fr.: système physique   

A set of physical components chosen to study their relations.

physical; → system.

fizikdân (#)

Fr.: physicien   

A specialist in → physics.

From physic, → physics, + → -ist.

Fizikdân, from fizik, → physics, + -dân "knower," present stem of dânestan "to know," → science.

fizik (#)

Fr.: physique   

The science that deals with matter and energy and their interactions.

M.E. fisyk(e), phisik(e), from O.Fr. fisique, from L. physica (fem. sing.) "study of nature," from Gk. physike episteme "knowledge of nature," from fem. of physikos "pertaining to nature," from physis "nature," from phyein "to bring forth, produce, make to grow," Gk. phy- "to become;" L. fui "I was," futurus "that is to be, future;" Ger. present first and second person sing. bin, bist; E. to be; O.Ir. bi'u "I am;" Lith. bu'ti "to be;" Rus. byt' "to be."

Loan from Fr. physique, as above.


Fr.: physisorption   

A kind of → adsorption in which the forces involved are → intermolecular  → van der Waals forces. Same as → physical adsorption. See also → chemisorption.

Physi-, from → physical; → sorption.

pi number
  عدد ِ پی   
adad-e pi (π)

Fr.: nombre pi (π)   

Symbol, π, for the ratio of the circumference of a circle to its diameter in Euclidean geometry; a fundamental mathematical constant, equal to 3.14159... π is an → irrational number (Lambert, 1761) and also a → transcendental number (von Lindemann, 1882). The most accurate determination of π prior to the Scientific Revolution belongs to the Iranian mathematician Jamshid Kashani, who gave 16 correct decimal places in A.D. 1424. With the advent of → calculus and more recently the invention of powerful computers, the decimal representation of π has now been computed to more than 1012 digits.

The π notation, representing the first letter of the Gk. word περιμετρον → perimeter, was first used by the British mathematician William Jones (1675-1749) in 1706. Its use was generalized after its adoption by the Swiss mathematician Leonard Euler (1707-1783) in 1737; → number.

Piazzi's Flying Star
  ستاره‌ی ِ پرنده‌ی ِ پیاتزی   
setâre-ye parande-ye Piazzi

Fr.: étoile volante de Piazzi   

Same as → 61 Cygni and → Bessel's star.

Giuseppe Piazzi (1746-1826) was the first to notice the large → proper motion of the star, in 1804. His observations over a period of 10 years revealed the largest proper motion ever detected for any star at the time, leading him to baptize it the "Flying Star;" → fly; → star.

Pickering series
  سری ِ پیکرینگ   
seri-ye Pikering (#)

Fr.: série de Pickering   

A series of → spectral lines of → singly ionized helium, observed in very hot → O-type and → Wolf-Rayet stars associated with transitions between the → energy level with → principal quantum number n = 4 and higher levels: n = 4-5 (10124 Å), n = 4-7 (5412 Å), n = 4-9 (4541 Å), n = 4-9 (4522 Å), and n = 4-11 (4200 ˚). The 4-6 (6560 Å) and 4-8 (4859 Å) transitions were originally not included in this series because they coincided with the hydrogen → Balmer series of lines and were thus obscured.

In honor of Edward C. Pickering (1846-1919), American astronomer and physicist; → series.

piko- (#)

Fr.: pico-   

A prefix denoting 10-12.

From It. piccolo "small."

Negârgar (#)

Fr.: Peintre   

The Painter's Easel. A faint constellation in the southern hemisphere, at 5h 30m right ascension, 50° south declination. Its brightest star is of magnitude 3.2. Its second brightest star, → beta Pictoris, is famous for its → circumstellar disk of gas and dust. Abbreviation: Pic; genitive: Pictoris.

Pictor, short for Equuleus Pictoris "painter's easel," from L. pictor "painter," from pingere "to make pictures."

Negârgar "painter," from negâr present stem of negâštan "to paint," negâr "picture, figure," from prefix ne- "down; into" (O.Pers./Av. ni- "down; into;" cf. Skt. ni "down," nitaram "downward;" Gk. neiothen "from below;" E. nether; O.E. niþera, neoþera "down, downward, below, beneath," from P.Gmc. *nitheraz; Du. neder; Ger. nieder; PIE *ni- "down, below") + gâr, from kar-, kardan "to do, to make" (Mid.Pers. kardan; O.Pers./Av. kar- "to do, make, build;" Av. kərənaoiti "he makes;" cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base kwer- "to do, to make").

fartur (#)

Fr.: image   

Any visible image, however produced. → photograph.

From L. pictura "painting," from pictus, p.p. of pingere "to make pictures, to paint."

Fartur "picture, image; reflexion, inversion" (Dehxodâ, Steingass); maybe from partow, → ray.


Fr.: par morceaux   

Denoting a function that is defined on a sequence of intervals or pieces. For example: |x| = -x for x < 0, x = 0 for x = 0, and x = x for x > 0.

From piece, → eyepiece, + -wise, → clockwise.

Tekke-yi, adj. of tekké "piece, patch."

piecewise continuous function
  کریای ِ پیوسته‌ی ِ تکه‌ای   
karyâ-ye peyvaste-ye tekke-yi

Fr.: fonction continue par morceaux   

A function f(x) in an interval if :1) the interval can be divided into a finite number of pieces in each of which f(x) is continuous, and 2) the limits of f(x) as x approaches the boundary point of each piece are finite. In other words, a piecewise continuous function is one that is made up of a finite number of continuous pieces.

piecewise; → continuous; → function.

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