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

1) To tell invented stories; create fables or stories filled with fantasy.
2) To relate an event as a fable.

→ fabulate; → -tion.

The act or process of facilitating.

→ facilitate; → -tion.

A set of distributions which have the same general mathematical → formula.

→ family; → distribution.

A classification scheme for distinguishing a → radio galaxy from an → active galaxy based on their → radio frequency  and → luminosity and their kpc-scale appearance. Analyzing a sample of 57 radio galaxies from the → 3CR catalogue, which were clearly resolved at 1.4 GHz or 5 GHz, Fanaroff & Riley (1974) discovered that the relative positions of regions of high and low → surface brightness in the → lobes of extragalactic → radio sources are correlated with their radio luminosity. They divided the sample into two classes using the ratio R_FR of the distance between the regions of highest surface brightness on opposite sides of the central galaxy or quasar, to the total extent of the source up to the lowest brightness contour in the map. → Fanaroff-Riley Class I (FR-I) , → Fanaroff-Riley Class II (FR-II). The boundary between the two classes is not very sharp, and there is some overlap in the luminosities of sources classified as FR-I or FR-II on the basis of their structures. The physical cause of the FR-I/II dichotomy probably lies in the type of flow in the → radio jets.

Bernard L. Fanaroff and Julia M. Riley, 1974, MNRAS 167, 31P; → classification.

The rotation of the plane of → polarization experienced by a beam of → linearly polarized radiation when the radiation passes through a material containing a magnetic field with a component in the direction of propagation. This effect occurs in → H II regions in which a magnetic field causes a change in the polarized waves passing through. Same as → Faraday effect.

→ farad; → rotation.

The induced → electromotive force in a circuit is equal in magnitude and opposite in sign to the rate of change of the → magnetic flux through the surface bounded by the circuit. Mathematically, it is expressed as: ∇ x E = -∂B/∂t, which is one of the four → Maxwell's equations.

→ farad; → law; → induction.

Biology: The act or process of fecundating.

→ fecundate; → -tion.

1) The act of federating or uniting in a league.
2) A political unit formed from smaller units on a → federal basis.

Verbal noun of → federate.

An old explanation, proposed by Enrico Fermi, of the → weak interaction.

→ fermi; → interaction.

An elementary particle, such as → electron, → proton, or → neutron, having a half integral value of → spin. Fermions obey the → Pauli exclusion principle.

From Fermi → fermi + → -on.

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.

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.

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.

→ field; → rotation.

A weak yet important kind of mixing that results from → fingering instability in stars within → radiative zones that have an unstable mean → molecular weight  → gradient. Also called → thermohaline convection.

→ finger; → -ing; → convection.

A → statistical population consisting of individuals or items which are finite in number.

→ finite; → population.

1) Generally, an expression to indicate that a comment or result is only approximate.
2) Math.: In calculus, limiting a differential equation to its → first derivative, for example: e^x≅ 1 + x. Also called → linear approximation.

→ first; → approximation.

A equation in which the highest → exponent of the → variable is 1. Same as → linear equation.

→ first; → degree; → equation.

A → differential equation containing only the first → derivative. For example, dy/dx = 3x and 2y(dy/dx) + 3x = 5.

→ first; → order; → differential; → equation.

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.