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

A ferroamagnetic substance, which possesses → ferromagnetism.

→ ferro-; → magnet.

Relative to or characterized by → ferromagnetism.

→ ferro-; → magnetic.

A property of certain substances which are enormously more magnetic than any other known substance. Ferromagnetic substances, such as the chemical elements iron, nickel, cobalt, some of the rare earths, and ceratin alloys, achieve maximum → magnetization at relatively low magnetic field strengths. Their large → magnetic permeabilityies (greater than unity) vary with the strength of the applied field. When the temperature of a ferromagnet is increased the property vanishes gradually due to randomizing effects of thermal agitation. Beyond a definite temperature for each substance ( → Curie temperature) it ceases to behave as a ferromagnet and becomes a → paramagnet. Ferromagnetism is due to the alignment of the → magnetic moments of uncompensated electrons in the crystal lattice. Under the influence of an external magnetizing field, all of the uncompensated electrons line up with their → spins in the direction of the field. In contrast with paramagnetic substances, in which spins interact only with an external magnetic field, in ferromagnets the spins interact with each others, each of them trying to align the others in its own direction. This coupling gives rise to a spontaneous alignment of the moments over macroscopic regions called domains. The domains undergo further alignment when the substance is subjected to an applied field. Ferromagnets retain their magnetisation even when the external magnetic field has been removed. See also → antiferromagnetism ; → diamagnetism; → magnetism.

→ ferro-; → magnetism.

Of or containing → iron, especially in the bivalent state. More specifically, iron with → oxidation number of +2, denoted iron(II) or Fe2+.

From L. ferrum "iron," + -ous a suffix forming adjectives that have the general sense "possessing, full of" a given quality.

Fervar, from fer, loan from Fr., + -var adj. suffix.

Iron in a plus-2 → oxidation state.

→ ferrous; → iron.

Physics: (of nuclear material) Able to become → fissile by → neutron capture.

M.E., from M.Fr. fertil, from L. fertilis "bearing in abundance, fruitful, productive," from ferre "to bear," from PIE root *bher- "to carry," also "to bear children," cognate with Pers. bordan "to carry, bear," → refer.

Bârvar, literally "fruitful," from bâr "fruit; flower; load; charge" + possession suffix -var, related to bordan "to bear, carry," as above.

An → isotope not itself → fissile but that is converted into a fissile isotope, either directly or after a short → decay process following absorption of a → neutron. Example: U-238 can capture a neutron to give U-239. U-239 then decays to Np-239 which in turn decays to fissile Pu-239. The most important fertile isotope is U-238. This is by far the most abundant isotope of natural uranium, making up 99.28%. The important transformation chain is: ₉₂U²³⁸ + ₀n¹→ ₉₃Np²³⁹ + β^- (23.5 minutes) → ₉₄Pu²³⁹ + β^- (2.36 days).

→ fertile; → isotope .

A schematic representation, in quantum electrodynamics and quantum chromodynamics, of the way elementary particles like electrons and protons interact with each other by exchanging photons. Use of Feynman diagrams can greatly reduce the amount of computation involved in calculating a rate or cross section of a physical process.

After the American physicist Richard P. Feynman (1918-1988), Nobel prize 1965; → diagram.

Same as → field horizontal branch star.

→ field; → horizontal; → branch; → star.

→ optical fiber.

From Fr. fibre, from O.Fr. fibre, from L. fibra "a fiber, filament," of uncertain origin, perhaps related to L. filum "thread."

Fibr, loan from Fr., as above.

One of the numbers in the → Fibonacci sequence.

→ Fibonacci sequence; → number.

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.

Anatomy: The outer and thinner of the two bones of the human leg, extending from the knee to the ankle.

Fom L. fibula "clasp, brooch; bolt, peg, pin," related to figere "to drive in, insert, fasten," → fix.

Nâzok-ney, literally "fine reed," from nâzok "→ fine" + ney "reed, pipe, flute."

1) Literary works invented by the imagination, such as novels or short stories.
2) An invented story or explanation; lie.
3) The act of inventing a story or explanation.
4) Law: Something assumed to be true for the sake of convenience, though probably false (Dictionary.com).

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.
2) Physics: A region or space defined by the presence of a physical force, such as electric, magnetic, or gravitational.
3) Math.: A mathematical entity for which addition, subtraction, multiplication, and division are well-defined.

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.

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.

→ field; → curvature.

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.

→ field; → equation.

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; → galaxy.

A → horizontal branch star with high velocity.

→ field; → horizontal; → branch; → star.