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

1) General: A device or a set of wires that receives or sends out radio signals.
2) In radio astronomy, the major dish-like component or wired structure used to collect radio signals.

L. antenna "sail yard," the long yard that sticks up on some sails, of unknown origin, perhaps from PIE base *temp- "to stretch, extend." In this sense, it is a translation of Gk. keraiai "horns" (of insects).

Âten, from Fr. antenne, from L. as above.

A measure of the directivity of a radio telescope. It is the ratio of the amount of power received in the direction the dish is pointing to the smaller amount of power from other directions in the sidelobes.

→ antenna; → gain.

A three-dimensional section of the → radiation pattern ofa directional antenna, bounded by one or more cones of nulls or by regions of diminished irradiance.

→ antenna; → lobe.

The response of an antenna to incident radiation as a function of the direction of incidence of the radiation. A generic antenna pattern consists of a → main lobe and a number of smaller → side lobes. Also called → radiation pattern.

→ antenna; → pattern.

In radio astronomy, a measure of the power absorbed by the antenna. In an ideal, loss-free radio telescope, the antenna temperature is equal to the brightness temperature if the intensity of the received radiation is constant within the main lobe. → antenna; → temperature.

antenna; → temperature.

The pair of colliding galaxies NGC4038 and NGC4039 and the long arcing insect-like "antennae" of luminous matter revealed by optical telescopes. The "antennae" are believed to have been produced by the collision between the galaxies that began about 100 million years ago and is still occurring. The Antennae Galaxies, about 60 million → light-years from Earth, lie in the constellation → Corvus.

Antennae, plural of → antenna; → galaxy.

Kahkešânhâ, plural of kahkešân→ galaxy; šâxak "insect antenna," from šâx "horn" (Mid.Pers šâk, cf. Skt. sakha- "a branch, a limb," Arm. cax, Lit. šaka, O.S. soxa, PIE *kakhâ "branch") + -ak suffix denoting relation, affinity, similarity (as in dastak, pos(tak, pas(mak, xarak, nâxonak, mus(ak, eynak);

The idea that the existence of → life and, in particular, our presence as → intelligent  → observers, → constrains the nature of the → Universe. It is an attempt to explain the observed fact that the → fundamental constants of nature are just right or fine-tuned to allow the Universe and life to exist. This is not however a "principle." See also → weak anthropic principle, → strong anthropic principle. Compare → Copernican principle.

Anthropic, from Gk. anthropikos "human," from anthropos "human being, man," → anthropo-; → principle.

Parvaz, → principle; ensân-hasti, from ensân, → anthropo-, + Mod.Pers. hasti "existence, being," Mid.Pers. astih, O.Pers. astiy; Av. asti "is," O.Pers./Av. root ah- "to be;" cf. Skt. as-; Gk. esti; L. est; PIE *es-.

A prefix with the meaning of "pertaining to man or human beings." Before a vowel, anthrop-. See also → man, → human. → anthropic principle.

Frpm Gk. anthropos "man, human being," from aner "man" (as opposed to a woman, a god, or a boy), from PIE *hner "man;" cf. Pers. nar "male," Skt. nara-, Welsh ner "man."

Ensân-, from ensân "mankind," loan from Ar. insân.

Prefix meaning "against, opposite of;" e.g. in → anticenter; → anticorrelation; → anticyclone; → antiparticle.

L. anti- from Gk. anti "against, opposite, instead of," from PIE *anti "against".

Pâd- "agaist, contrary to," from Mid.Pers. pât- "to, at, for, in," from O.Pers. paity "agaist, back, opposite to, toward, face to face, in front of;" Av. paiti; cf. Skt. práti "toward, against, again, back, in return, opposite;" Pali pati-; Gk. proti, pros "face to face with, toward, in addition to, near;" PIE *proti.

The → antiparticle of a → baryon.

→ anti-; → baryon.

The point in the → Galactic plane that lies directly opposite the → Galactic center. It lies in → Auriga at approximately R.A. 5h 46m, Dec. +28° 56'; the nearest bright star to it is → Alnath in → Taurus.

Anticenter, from → anti- + → center.

Pâdmarkaz, from pâd-, → anti-, + markaz, → center.

Meteorology: Small, faintly colored rings of light surrounding the → antisolar point, seen when looking down at a water cloud. Same as glory.

Anticorona, from → anti- + → corona.

Pâdafsar, from pâd-, → anti- + afsar "corona."
Šokuh "glory."

Statistics: The correlation coefficient of two random variables X and Y is in general defined as the ratio of the Cov(X,Y) to the two standard deviations of X and Y. It varies between 1 and -1 corresponding to complete correlation or anticorrelation.

Anticorrelation, from → anti- + → correlation.

Pâdhambâzâneš, from pâd-, → anti-, + hambâzâneš, → correlation.

Rays of → sunlight that appear to converge at the → antisolar point. Like → crepuscular rays, they are parallel beams of sunlight from holes in the clouds, and their apparently odd directions are a perspective effect.

→ anti-; → crepuscular rays.

Meteo.: A weather phenomenon associated with atmospheric high pressure. In the Northern Hemisphere an anticyclone rotates in the clockwise direction. The rotation is caused by the movement of colder higher pressure air that is moving away from the poles toward the equator being affected by the rotation of the Earth.

→ anti-; → cyclone.

Having a sense of rotation about the local vertical opposite to that of the Earth's rotation. In other words, → clockwise in the Northern Hemisphere, → counterclockwise in the Southern Hemisphere, and undefined at the equator. The opposite of → cyclonic (Meteorology Glossary, American Meteorological Society).

→ anticyclone; → -ic.

The function F(x) is called the antiderivative of the function f(x) on the interval [a,b] if at all points of this interval F'(x) = f(x). Same as primitive.

→ anti- + → derivative.

Karyâ, → function; noxostin "primitive," → first.

A property possessed by some → metals, → alloys, and salts of transition elements in which there is a lack of → magnetic moment due to the antiparallel or spiral arrangement of atomic → magnetic moments.

→ anti- + → ferromagnetism.

An atom made from an → antiproton and a → positron. In 2010 a research collaboration at CERN combined decelerated antiprotons with positrons to produce antihydrogen atoms. They managed 38 times to confine single antihydrogen atoms in a magnetic trap for more than 170 milliseconds (Andersen et al. 2010, Nature, 17 Nov.).

→ anti- + → hydrogen.

A unique Greek geared device, constructed around the end of the second century BC to display the movement of the Sun, the Moon, and possibly the planets around the Earth, and predict the dates of future eclipses. It measures about 32 by 16 by 10 cm and contains at least 30 interlocking gear-wheels, all of them having triangular teeth, from 15 to 223 in number. This device is one of the most stunning artefacts remained from antiquity, revealing an unexpected degree of technical creativity for the period. Nothing close to its technological sophistication appears again for well over a millennium, when astronomical clocks appear in the medieval Europe. It was discovered in 1901 in a sunken ship just off the coast of Antikythera, an island between Crete and the Greek mainland. Its significance and complexity were not understood until decades later. After lots of study involving several research fields, a copy of the device has recently been constructed. See, e.g., Freeth et al. 2006, Nature 444, 587.

Named after the Greek island in the Ionia Sea from which the fragments of the device were discovered in 1901 by sponge divers, who found a sunken Roman ship. Several pieces of evidence indicate that the Roman ship carrying the device wrecked sometime shortly after 85 BC. The ship also contained an enormous booty of bronzes, glassware, jewelry and pottery; → mechanism.