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

Lack of → validity.

→ invalid; → -ity.

Mechanics: For a rotating rigid body not subject to external torque, a plane which is perpendicular to the angular momentum vector of the body, and which is always tangent to its → inertia ellipsoid.

Invariable negation of → variable; → plane.

Any property of a physical law or quantity that is unchanged after the application of certain classes of transformations.

Invariance; noun of → invariant.

A quantity which is independent of the coordinate system. For example the vector product of two vectors is an invariant since it depends only on the magnitude of the two vectors and the angle between them.

From negation prefix → in- + variant, from L. variantem (nom. varians), pr.p. of variare "to change," from varius "varied, different, spotted."

Nâvartâ, from negation prefix nâ-, → in-, + vartâ adj., from vartidan, variant of gardidan, gaštan "to change; to turn," Mid.Pers. vartitan; Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend."

To create or design a new type of thing (process, machines, etc.). See also → discover.

From L. inventus, p.p. of invenire "to encounter, come upon, find," from in- "upon" + ven-, from venire "to come" + -tus p.p. suffix.

Parâvidan on the model of dialectals Munji purôv-/purvi-, Yidgha pura-/prvei- "to find, obtain," Shughni, Roshani, Bartangi, Yazghulami firâp-fiript "to arrive at, reach;" prefixed (*fra-/*pra-) from Proto-Iranian *Hap/f- "to reach, attain;" cf. Av. ap- "to reach, attain;" related to Pers. yâb-, yâftan "to find" (Cheung 2007).

The action or of inventing or something invented.

Verbal noun of → invent.

A person who invents.

→ invent + → -or.

Opposite to or reversing something.
Math.: Involving two variables that are in a mathematical relationship where, when one increases, the other decreases and vice versa.

From L. inversus, p.p. of invertere, → invert.

Vârun "inverse, upside down," from vâ- "back, backward, again, re-," variant of bâz-, from Mid.Pers. abâz-, apâc-, O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from," apaš [adv.] "toward the back;" cf. Skt. ápāñc "situated behind."

A basic rule in → group theory stating that for any element a of a group there is an element a^-1 such that a * a^-1 = a^-1 * a = e.

→ inverse; → axiom.

A collision of a proton with an electron that produces a neutron and an electron neutrino. See → beta decay.

→ inverse; β, letter of Gk. alphabet; → decay.

The absorption of a photon by an electron in a strong electric field. → bremsstrahlung.

→ inverse; → bremsstrahlung.

A → scattering process by which fast-moving, energetic particles transfer energy to photons, decreasing the wavelength of the radiation. This is a particularly important effect in astrophysics and cosmology since it explains the → Sunyaev-Zel'dovich effect.

→ inverse; → Compton effect.

A line profile in which the emission is on the blue side of the absorption. It is usually interpreted as the redshift of the absorption component relative to emission lines, which necessitates infall of matter.

→ inverse; → P Cygni; → line; → profile.

A force law that applies to the → gravitational and → electromagnetic forces in which the magnitude of the force decreases in proportion to the inverse of the square of the → distance.

→ inverse; → square; → law.

The → Zeeman effect obtained in absorption. The phenomenon is observed by sending white light through an absorbing vapor when the latter is subjected to a uniform magnetic field. The laws governing the inverse effect are similar to those for the direct effect.

→ inverse; → Zeeman effect.

Meteo.: A departure from the usual decrease or increase with altitude of the value of an atmospheric property. It almost always refers to a temperature inversion, i.e., an increase in temperature with altitude. Chemistry: To subject to → inversion.

Verbal noun of → invert.

Meteo.: The atmospheric layer in which the temperature gradient is inverted, that is increases; → inversion. The inversion layer tends to prevent the air below it from rising, thus trapping any pollutants that are present.
Electricity: A converting of direct current into alternating current.

→ inversion; → layer.

To turn upside down.
To reverse in position, order, direction, or relationship. → inversion layer.

From M.Fr. invertir, from L. invertere "turn upside down, turn about," from → in- "in, on" + vertere "to turn;" cf. Pers. gardidan, gaštan "to turn, to change;" Mid.Pers. vartitan; Av. varət- "to turn, revolve;" Skt. vartati; O.H.G. werden "to become;" PIE base *wer- "to turn, bend."

Vâgardândan, from vâ-, → re-, + gardândan, from gardidan "to turn; to change," from Mid.Pers. vartitan; Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend."
Vârunidan, infinitive of vârun, → inverse.

In atomic physics, a condition in which there are more electrons in an upper energy level than in a lower one, while under normal conditions of thermal equilibrium the reverse is true. → optical pumping.

Inverted, p.p. of → invert; → population.

Fluid mechanics: Having no → viscosity. Same as → nonviscous.

From → in- "non-" + viscid, from L.L. viscidus, from vis(cum) "anything sticky, mistletoe," → viscous, + -idus.