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

The state of a → physical system regarding its temperature, density, pressure, etc. at a given time.

→ physical; → condition.

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

→ physical; → constant.

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.

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.

A real periodic variation in the rotation rate of a celestial object, as distinct from a → geometrical libration. In particular, slight oscillations in the → Moon's rotation caused by the → gravitational attraction of the Earth on the → equatorial bulge of the Moon's near side. The Moon's physical libration is about 0.03° in longitude and about 0.04° in latitude.

→ physical; → libration.

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.

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.

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

→ physical; → phenomenon.

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

→ physical; → quantity.

A set of physical components chosen to study their relations.

→ physical; → system.

A specialist in → physics.

From physic, → physics, + → -ist.

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

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.

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.

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.

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.

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.

A prefix denoting 10^-12.

From It. piccolo "small."

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 k^wer- "to do, to make").

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.

1) A portion of an object or of material, produced by cutting, tearing, or breaking the whole.
2) An item forming part of a set.
3) A written, musical, or artistic creation (OxfordDictionaries.com).

M.E. pece, peece, from O.Fr. piece, from V.L. *pettia, probably from Gaulish (cf. Welsh peth "thing;" Breton pez "piece").

Teké "piece, patch."