Fr.: suite de Fibonacci
An infinite sequence of integers, starting with 0 and 1, where each element is the sum of the two previous numbers. For example: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ... As the sequence develops, the ratio of the consecutive terms converges to the → golden ratio, about 1.618.
Leonardo Pisano Fibonacci (1170-1250), medieval Italian mathematician who wrote Liber abaci (1202; Book of the Abacus), the first European work on Indian and Arabian mathematics, which introduced "Arabic" numerals in Europe; → sequence.
A linear pattern in the → chromosphere of the → Sun, as seen through an → H-alpha filter, occurring near strong → sunspots and → plages or in → filament channels. They are magnetically confined tubes of hot → plasma. Individually, they are about 10,000 km long and last for 10 to 20 minutes.
From Mod.L. fibrilla, from fibr(a) "fiber" + -illa diminutive suffix.
Târcé, from târ "thread, warp, → string" + diminutive suffix -cé, from Mid.Pers. -cak, variants -êžak (as in kanicak "little girl," sangcak "small stone," xôkcak "small pig"), also Mod.Pers. -ak.
1) Literary works invented by the imagination, such as novels or short stories.
M.E., from O.Fr. ficcion "dissimulation, ruse; invention, fabrication" and directly from L. fictionem "a fashioning or feigning," noun of action from p.p. stem of fingere "to shape, form, devise, feign," originally "to knead, form out of clay," from PIE *dheigh- "to build, form, knead;" akin to Skt. dehah "body," literally "that which is formed," dih- "to besmear;" Gk. teikhos "wall;" L. fingere "to form, fashion," Gothic deigan "to smear;" O.Irish digen "firm, solid."
Formed on the model of fiction, as above, from diz- "to build, to form;" (related to Pers. dež, dez "fortress"); cf. Mid.Pers. dys-/dēs- "to build;" Sogd. dys "to build;" Av. (+ *pari-) daēz- "to build (around);" Proto-Ir. *daiz- "to build, form;" from PIE *dheigh- "to build, form," as above, + suffix -an.
1) General: An expanse of anything.
M.E., from O.E. feld "plain, open land," probably related to O.E. folde "earth, land," from P.Gmc. *felthuz "flat land" (cf. Ger. Feld), from PIE *pel(e)-tu-,from base *pele- "flat, to sprea;" cf. L. planus "flat, level," → plane.
Meydân "field, field of battle, arena, extensive plain," from Mid.Pers. mêdân "arena, field." This term is loaned into Ar. from Pers. or Mid.Pers.
xamidegi-ye meydân (#)
Fr.: courbure de champ
An aberration in an optical instrument, common in Schmidt telescopes, in which the focus changes from the center to the edge of the field of view. Owing to this aberration, a straight object looks curved in the image.
Fr.: équation de champ
In a physical theory, an equation that describe how a fundamental force interacts with matter. Einstein's equations of → general relativity are called field equations since they describe the → gravitational field. Similarly, → Maxwell's equations describe the electromagnetic field.
Fr.: galaxie de champ
A galaxy that lies in the direction of a → cluster of galaxies, but is not a member of the cluster. Field galaxies are rare, less than about 5% of all galaxies.
field horizontal branch star
setâre-ye šâxe-ye ofoqi-ye meydâni
Fr.: étoile de la branche horizontal du champ
A → horizontal branch star with high velocity.
Fr.: lentille de champ
A lens placed at or near the focal plane of a telescope to create an image of the primary mirror inside the instrument.
field O star
setâre-ye O-ye meydân
Fr.: étoile O de champ
An → O-type star which is apparently not associated with a → star cluster. A significant fraction of → massive stars in the → Milky Way and other galaxies are located far from star clusters and → star-forming regions. It is known that some of these stars are → runaways, i.e. possess high → space velocities (determined through the → proper motion and/or → radial velocity measurements), and therefore most likely were formed in embedded clusters and then ejected into the field because of dynamical interactions or → binary-→ supernova explosions. However, there exists a group of field O stars whose runaway status is difficult to prove via direct proper motion measurements or whose low space velocities and/or young ages appear to be incompatible with their large separation from known star clusters. The existence of this group led some authors to believe that these stars can form → in situ. The question of whether or not O stars can form in isolation (→ isolated massive star formation) is of crucial importance for → star formation models (Gvaramadze et al., 2012, MNRAS, 424, 3037).
Fr.: objet de champ
An astronomical object that is seen in the direction of a group but not physically belonging to the group. → field galaxy.
field of force
meydân-e niru (#)
Fr.: champ de force
field of view
meydân-e did (#)
Fr.: champ de vue
The entire angular expanse of the sky viewed by an optical instrument.
Fr.: rotation de champ
The effect of the Earth's rotation on the position of the image formed on the → focal plane of a telescope during long exposures. In the case of → equatorial mounting, the image remains fixed, whereas it turns continuously with an → altazimuth mounting. In the latter case the image motion must be compensated by an appropriate mechanism, → field rotator.
Fr.: rotateur de champ
A device used on a telescope to correct for the → field rotation while tracking an object.
Fr.: étoile de champ
A star that does not belong to a stellar cluster, but happens to be adjacent to it.
Fr.: diaphragme de champ
A diaphragm located at an image plane of an optical system that determines the size and shape of the image. → aperture stop.
Fr.: théorie des champs
1) A theory which uses the concept of → field
to describe physical phenomena. It consists of two types:
→ classical field theory
and → quantum field theory.
The precise curve required on the surface of an optical element, especially the mirror of a reflecting telescope.
From O.Fr. figure, from L. figura "a shape, form."
Šekl from Ar. šakl "figure."
Figuring, noun of → figure.
Šekldahi, "giving form," from šekl, → figure + dahi, a verbal noun of dâdan "to give," from Mid.Pers. dâdan "to give," O.Pers./Av. dā- "to give, grant, yield," dadāiti "he gives;" cf. Skt. dadáti "he gives," Gk. didomi "I give," tithenai "to put, set, place;" L. dare "to give, offer;" facere "to do, to make;" Rus. delat "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do." PIE base *dhe- "to put, to do."