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

A process of reduction to linear form by appropriate change of variables or by approximation.

Verbal noun of → linearize.

A differential equation that has been derived from an original nonlinear equation.

Linearized, p.p. of → linearize; → differential; → equation.

A large, usually tawny-yellow cat, Panthera leo, native to Africa and southern Asia, having a tufted tail and, in the male, a large mane (dictionary.com).

M.E., from O.Fr., variant of leon, from L. leon- (stem of leo), from Gk. leon.

Mid.Pers. šagr "lion;" cf. Parth. šarg; Sogd. šarγu "lion;" its O.Pers. and Av. forms are not extant. Šir may be cognate with Skt. kēsarin- "lion; literally maned," from kēsar- "mane;" PIE *kaisar- "mane; hairs." If so, šir could be related to PIE *kaisaraka-, provided that the the initial *kai- is dropped and *saraka- has transformed in *sarg, šarg, šir.

1) The act or process of liquefying or making liquid.
2) The state of being liquefied.

→ liquefy; → -tion.

→ Einstein equivalence principle.

→ local; → position; → invariance.

The condition of the wave-function of an electron if it is confined to a small region of a large system rather than being extended through the system.

Verbal noun of → localize.

Same as → reddening coefficient.

→ logarithmic; → extinction.

A symbol that can be combined with one or more → sentences in order to form a new sentence. For example "and" (∧), "or" (∨) "not" (¬), "if-then" (→), and "iff" (⇔).

→ logical; → connective.

A → probability distribution in which the natural logarithm (logX) of the → random variable (X) has a → Gaussian distribution.

→ logarithm; → normal distribution.

1) Having considerable linear extent in space. → very-long-baseline interferometry (VLBI).
2) Having considerable duration in time. → long-period variable.

M.E. longe, O.E. lang, long, akin to O.H.G., Ger. lang "long," O.N. langr, M.Du. lanc, Goth. laggs "long," L. longus, → longitude.

Derâz "long," Mid.Pers. drâz "long;" O.Pers. darga- "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "lon (in space and time)."

A comet with orbital period of more than 200 years. → short-period comet; → periodic comet.

→ long; → period; → comet.

A type of → variable star in which variations in brightness occur over long time-scales of months or years. The term generally refers to → Mira variable types.

→ long; → period; → variable.

The angular distance on the Earth's surface, measured east or west from the prime meridian at Greenwich to the meridian passing through a position, expressed in degrees (or hours), minutes, and seconds.

L. longitudo "length," from longus "long," cognate with Pers. derâz, as below, Gk. dolikhos "elongated;" O.H.G., Ger. lang, O.N. langr, M.Du. lanc, Goth. laggs "long;" PIE base *dlonghos- "long."

Derežnâ, from derež (Kurdi, Laki), variants darg "length; long, tall" (Zâzâ), darγ (Ossetic), derâz "long" + -nâ noun forming suffix from adjective, as in derâznâ, pah(n)nâ, farâxnâ, tangnâ, tiznâ. The first element from Mid.Pers. drâz "long;" O.Pers. darga- "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "long (in space and time);" PIE *dlonghos- "long," as above.

One of the → orbital elements used to specify the orbit of an object in space. It is the angle from the reference direction, called the origin of longitude, to the direction of the → ascending node, measured in the reference plane.

→ longitude; → ascending node.

Of or pertaining to longitude or length. Extending in the direction of the length.

Adj. of → longitude.

1) A → magnetic field whose lines of force (→ line of force) run parallel to the long axis of the → magnet. Longitudinal magnetization of a component can be accomplished using the longitudinal field set up by a → coil or → solenoid. It can also be accomplished using permanent magnets or electromagnets.
2) In → stellar magnetic field observations, the magnetic field along the → line of sight.

→ longitudinal; → magnetic; → field.

In special relativity theory, the mass of a body when the acceleration is parallel or anti-parallel to velocity: m_l = m₀ / [1 - (v/c)²]^3/2, where m₀ is the → rest mass, v is the velocity, and c the → velocity of light. → transverse mass.

→ longitudinal; → mass.

A wave vibrating along the direction of propagation, such as a → sound wave. → transverse wave.

→ longitudinal; → wave.

The → Zeeman effect when the emitting source is viewed in the direction of the magnetic field. In the normal longitudinal effect, each spectral line is split into two components with frequencies ν ± Δν. The line with the frequency ν - Δν shows left-hand → circular polarization and that with frequency ν + Δν shows right-hand circular polarization. → transverse Zeeman effect.

→ longitudinal; → Zeeman effect.

The decrease in the length of a body moving in the direction of its length as measured by an observer situated in that direction. The shortening factor is [1 - (v/c)²]^1/2, where v is the relative velocity and c light speed.

→ Lorentz; → contraction.