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

Same as → first-order logic.

→ first; → order; → predicate; → calculus.

An optical spectrum, produced by a diffraction grating, in which the difference in path length of light from adjacent slits is one wavelength.

→ first; → order; → spectrum.

A limbless cold-blooded vertebrate animal with gills and fins living wholly in water (OxfordDictionaries.com).

M.E. fis(c)h, fyssh, O.E. fisc; cognate with Du. vis, Ger. Fisch, O.Norse fiskr, Goth. fisks; akin to L. piscis; PIE root *pisk- "a fish."

Mâhi "fish," from Mid.Pers. mâhik; Av. masya-; cf. Skt. matsya-, Pali maccha-.

Any material that is capable of undergoing → nuclear fission by → thermal neutrons. The three primary fissile materials are uranium-233, uranium-235, and plutonium-239. Although sometimes used as a synonym for → fissionable material, this term has acquired a more restricted meaning.

From L. fissilis, from fiss(us), + -illis a suffix of adjectives expressing capability, susceptibility, liability, aptitude, etc.

Šekâftani, from šekâft, → fission + -i a suffix expressing capability, aptitude, etc.

An isotope that is capable of undergoing nuclear fission after capturing either fast neutron or thermal neutron. Typical fissionable isotopes: ²³⁸U, ²⁴⁰Pu, but also ²³⁵U, ²³³U, ²³⁹Pu, ²⁴¹Pu

→ fissile; → isotope .

1) The act or process of splitting or breaking into parts.
2) Splitting of the nucleus of an atom into two or more fragments of comparable size, usually as the result of the impact of a neutron on the nucleus. Same as → nuclear fission.

Fission, from L. fissionem "a breaking up, cleaving," from root of findere "to split."

Šekâft, stem of šekâftan "to split, break, tear," akin to kaftan, kâftan "to split; to dig," Parthian Mid.Pers. q'f- "to split;" Sogdian kβ "to split;" Chorasmian kf- "to split, be split;" Proto-Iranian *kap-, *kaf- "to split."

Nuclides generated by the fission of higher mass elements or by subsequent radioactive decay of nuclides directly generated by fission.

→ fission; → product.

A theory that suggests the Moon was formed at the same time as Earth. A spinning Earth ejected a large piece of its material into space which then developed into the shape and orbit of the Moon. This event was also thought to be at the origin of the Pacific Ocean. This first modern idea about the formation of the Moon is due to George Darwin, the son of the great naturalist Charles Darwin. The fission theory explained the lack of volatile substances on the Earth. The volatile materials on the Earth would have been thrown out into space The fission theory is almost completely abandoned today. The analysis of lunar rocks brought to Earth by NASA astronauts showed that the Moon rocks are older than the rocks at the bottom of the Pacific Ocean. Moreover, modern → plate tectonics gives a better explanation of the origin of the Pacific Ocean. See also → giant impact hypothesis, → capture theory, → co-formation theory.

→ fission; → theory.

The material that can be fissioned by fast neutrons, such as uranium-238. Commonly used as a synonym for → fissile material.

From → fission + → -able.

1) (v.) To pass a mathematical line or curve through data points.
2) (n.) The act of fitting.

From M.E. fitten; akin to M.Du. vitten "to befit."

Saz, from sazidan "to suit, fit, be worthy," sazâ "suitable, agreeing with, congruous, deserving of," Mid.Pers. sacitan/sazidan "to fit," sazešn "fitness," sazâg "fitting, worth;" Av. ¹sak- "to understand or know a thing; to mark;" cf. Skt. śak- "to be able, powerful" śakta- "able, competent," śakti- "ability, power;" alternatively from Av. ²sak- "to go by, pass, pass away; to be up or over (of time)."

The process or instance of adapting a mathematical curve to data points.

Verbal form of → fit.

The discrepancy between the mathematical curve and data points. → fit.

→ fitting; → error.

A cardinal number whose symbol is 5, V, or ۵.

Five, from O.E. fif, from P.Gmc. *fimfe (cf. O.S. fif, O.H.G. funf), from PIE *penk^we "five;" cognate with Pers. panj, as below.

Panj, from Mid.Pers. panj; Av. panca; cf. Skt. páñca; Gk. pente; L. quinque; E. five, as above.

A photometric system which uses five filters, from ultraviolet to the red part of the visual spectrum: U, B, V, R and I.

→ five; → color; → system.

The 500 m diameter → radio telescope which is the largest → single-dish antenna in the world. It is an Arecibo type telescope nestled within a natural basin in China's remote and mountainous Dawodang, Kedu Town, in southeastern China's Guizhou Province. The → reflector consists of 4,450 triangular panels, each with a side length of 11 m. More than 2,000 → actuators are used, according to the feedback from the measuring system, to deform the whole reflector surface and directly correct for → spherical aberration. Several detectors are used to cover a frequency range of 70 MHz to 3 GHz.

→ five; → hundred; → meter; → aperture; → spherical; → radio; → telescope.

1) To make fast, firm, or stable.
2) To place definitely and more or less permanently (Dictionary.com).

M.E. fixen, probably from O.Fr. fixe "fixed," from L. fixus "fixed, fast, established, settled," p.p. of figere "to fix, fasten."

Infinitive, from barjâ, → fixed.

The act of fixing or the state of being fixed.

Verbal noun of → fix; → -tion.

1) Fastened, attached, or placed so as to be firm and not readily movable; firmly implanted; stationary; rigid.
2) Rendered stable or permanent, as color.
3) Set or intent upon something; steadily directed (Dictionary.com).

Past participle from → fix.

Barjâ "fixed; in place; properly placed," from bar "on, upon, up," → object, + jâ, → place,

A → heavenly body that, in → contrast to the → planets, does not appear to change its relative → position on the → celestial sphere.

Fixed, p.p. of → fix; → star.

Setâré, → star; barjâ, → fixed.
Istâdé (Biruni in at-Tafhim) "standing," from istâdan "to stand;" O.Pers./Av. sta- "to stand, stand still; set" (cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh;" stasis "a standing still;" Lith. statau "place;" Goth. standan; L. stare "to stand;" PIE base *sta- "to stand");
Biyâbâni (Biruni in at-Tafhim), from Mid.Pers. awiyâbânig "fixed," from negation prefix → a- + wiyâbânig "wandering," from wiyâbân "deluded, seduced," wiyâbânênidan "to lead astray, deceive," from Av. vi- "apart, away from, out" (O.Pers. viy- "apart, away;" cf. Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + dab- "to deceive;" cf. Skt. vimugdha- "confused, bewildered," vimohita- "confused, infatuated." Note that biyâbân "desert" is from an other origin.

The determination of the shape of an optical surface by means of → interferometry using a → fringe pattern formed with respect to a reference surface.

Named after the French physicist Armand Hippolyte Louis Fizeau (1819-1896), see also → toothed-wheel experiment; → test.