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

A philosophical doctrine that holds that → reason alone, unaided by experience, can arrive at basic truth regarding the world.

From → rational + -ism a Gk. suffix used in the formation of nouns denoting action or practice, state or condition, principles, doctrines, and so forth.

Râyan, → reason; xerad, → rational; bâvari, from bâvar "belief" (Mid.Pers. wâbar "beleif;" Proto-Iranian *uar- "to choose; to convince; to believe;" cf. Av. var- "to choose; to convince" varəna-, varana- "conviction, faith;" O.Pers. v(a)r- "to choose; to convince;" Skt. vr- "to choose," vara- "choosing").

The operation of a computer during the actual time that the related physical processes take place so that the results can be used to guide the physical processes.

→ real; → time; → operation.

1) Act of regenerating; state of being regenerated.
2) Electronics: A feedback process in which energy from the output of an amplifier is fed back to the grid circuit to reinforce the input.
3) Biology: The restoration or new growth by an organism of organs, tissues, etc., that have been lost, removed, or injured (Dictionary.com).

→ re-; → generation.

1) The act or instance of registering.
2) An entry in a register (Dictionary.com).

→ register; → -tion.

The aberration of light for an object moving with → relativistic speed. In contrast to the classical case, the → Lorentz transformation between the → rest frame of the observer and that of the object must be used. Relativistic aberration is expressed by the equation: cos φ' = (cos φ - )/(1 - cos φ.v/c), where φ is the classical → aberration angle, v the speed of the Earth, and c the → speed of light. It can also be expressed as: tan φ' = -(c/v)(1 - v²/c)^1/2.

→ relativistic; → aberration.

The act or process of restoring such as → image restoration.

Verbal noun of → restore.

An acceleration that results from the vector addition of two or more distinct accelerations.

→ resultant; → acceleration.

The spectrum of a molecule resulting from the simultaneous rotation and vibration of its constituent atoms.

→ rotation; → vibration; → spectrum.

Physics: Degree of magnetization of a substance which cannot be exceeded however strong the applied magnetizing field.
Detectors: The condition of a detector or a pixel when it is submitted to a signal so strong that it cannot handle it properly; the result is a non-linear, useless response.

Verbal noun of → saturate.

The maximum current that can be obtained in a specific circuit under specified conditions.

→ saturation; → current.

The maximum intrinsic magnetic induction possible in a material.

→ saturation; → induction.

In radar, a signal whose amplitude is greater than the dynamic range of the receiving system.

→ saturation; → signal.

A star whose formation is induced by an older star itself formed previously in the same region. See also → stimulated star formation, → sequential star formation, → triggered star formation.

→ second; → generation; → star.

The smallest component of the aberration of starlight which is caused by the motion of the solar system through space. → annual aberration; → diurnal aberration.

→ secular; → aberration.

The apparent gradual increase in the → Moon's motion in its orbit, as measured relative to → mean solar time. Secular acceleration corresponds to an extremely gradual reduction in the speed of the → Earth's rotation. The slow-down of the Earth's spin comes mainly from → tidal frictions from the Moon. Historically, Edmond Halley (1656-1742) was the first to suggest that the Moon's mean rate of motion relative to the stars was gradually increasing. In 1693, Halley compared eclipses of recent, medieval, and classical Babylonian time, and discovered that the Moon's mean motion had been gradually increasing. Using Lunar Laser Ranging measurement, based on laser reflectors left by the Apollo astronauts on the Moon's surface (1969 to 1972), the secular acceleration is derived to be -25".4 ± 0".1 century ² (Xu Huaguan et al., 1996, in Earth, Moon and Planets 73, 101). This corresponds to a linear increase of about 3.5 cm yr^-1 in the mean Earth-Moon distance.

→ secular; → acceleration.

General: The act or process of separating. The place at which a division or parting occurs.
Astro.: The angular distance between the two components of a visual binary or optical double star.

M.E., from O.Fr. separation, from L. separationem, from separare "to pull apart," from se- "apart" + parare "make ready, prepare."

Jodâyi state noun of jodâ "separate," from Mid.Pers. yut "separate, different;" Av. yuta- "separate, apart."

The energy required to remove a particle (a proton or a neutron) from a particular atomic nucleus.

→ separation; → energy.

Same as the → Shapley supercluster.

→ Shapley's wing; → concentration

Concept used to quantify the effects of noise. It is the ratio of a signal to the standard deviation of the signal.

→ signal; → noise; → ratio.

An aberration of a spherical lens or spherical mirror in which light rays converge not to a single point but to a series of points with different distances from the lens or mirror. Spherical aberration is corrected by using parabolic reflecting and refracting surface.

→ spherical; → aberration.