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

A faint glow of light in the night sky seen exactly opposite the Sun. The gegenschein is sunlight back-scattered off millimeter-sized dust particles along the ecliptic. In comparison with zodiacal light (forward-scattered sunlight), which is triangular in shape and found near the horizon, the gegenschein is roughly circular. Same as counterglow.

Gegenschein, from Ger. gegen "counter, opposed to" (O.H.G. gegin, gagan, M.Du. jeghen, E. against, again) + Schein "glow, shine" (M.H.G. schinen, O.H.G. skinan, P.Gmc. *skinanan; E. shine; cf. Mod.Pers. sâyé "shadow;" Mid.Pers. sâyak "shadow;" Av. a-saya- "throwing no shadow;" Skt. chāya- "shadow;" Gk. skia "shade;" Rus. sijat' "to shine;" PIE base *skai- "bright").

Pâdfrouq "counterglow," from pâd- "agaist, contrary to" (from Mid.Pers. pât-; 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) + foruq "light, brightness" (related to rôšan "light; bright, luminous;" ruz "day," afruxtan "to light, kindle;" Mid.Pers. payrog "light, brightness," rošn light; bright," rôc "day;" O.Pers. raucah-; Av. raocana- "bright, shining, radiant," raocah- "light, luminous; daylight;" cf. Skt. rocaná- "bright, shining, roka- "brightness, light;" Gk. leukos "white, clear;" L. lux "light" (also lumen, luna; E. light, Ger. Licht, and Fr. lumière; PIE base *leuk- "light, brightness").

A device for detecting ionizing radiations, whether corpuscular (α-, β-particles), or electromagnetic (X- and gamma-rays). It consists essentially of a fine wire anode (e.g., tungsten) surrounded by a coaxial cylindrical metal cathode, mounted in a glass envelope containing gas at low pressure. A large potential difference (800 to 2000 volts) is maintained between the anode and the cathode. The ionizing particle can enter through a thin glass or mica window. The particle produces ionization of gas molecules. The ions are accelerated by the electric field and produce more ions by collisions, causing the ionization current to build up rapidly. The current, however, decays quickly since the circuit has a small time constant. There is therefore a momentary potential surge which may be amplified and made to actuate a relay to advance a mechanical counter, or to produce a click in a loudspeaker. Same as Geiger-Mulle counter.

Named after Hans Geiger (1882-1945), the German physicist, who invented the instrument. He is also known for his work on atomic theory and cosmic rays; → counter.

To castrate (an animal, especially a horse).

M.E. gelden, from O.Norse gelda, ultimately from PIE *ghel- "to cut."

Axtan, variant of âxtan, âhixtan, âhiz- "to draw out; castrate, geld," → object.

A castrated male animal, especially a horse.

→ geld; → -ing.

A bright → gamma-ray source discovered in 1973 in the constellation → Gemini with instruments aboard NASA's first γ-ray satellite SAS-2. It was known only as a γ-ray source until it was detected in X-rays by the Einstein Observatory and associated with an optical counterpart of apparent magnitude 25. Because its luminosity outside of the γ-ray region is extremely low, the nature of this object remained a mystery until the discovery of pulsed emission, by the → ROSAT satellite in 1992, showed that it is a → pulsar. The pulsar period (~237 milliseconds) and its → period derivative (~1.1 × 10^-14 s s^-1) correspond to a → spin-down age of ~340,000 years. Also called PSR J0633+1746 (see Bignami & Caraveo 1996, ARA&A 34, 331 for a review).

An abbreviation for the Gemini gamma ray source. More amusingly, Geminga has been related to the Italian dialectal ghè minga spoken by the involved astronomers. This, in Milanese, means "it's not there," referring to the fact that the source could not be detected in the radio frequencies, one of the ongoing enigmas.

The Twins. A prominent constellation of the northern hemisphere and the third (and northernmost) of the → Zodiac. It lies south and east of → Auriga, west of → Cancer, and north and east of → Orion, at 7h right ascension and +22° declination. Its brightest stars are → Castor and → Pollux. Abbreviation: Gem; genitive: Geminorum.

Gemini, from M.E., from L. gemini, plural of geminus "twin; double;" cf. Av. yəma- "twin;" Skt. yamá-, yamala- "twin, paired;" Persian dialects Kermâni jomoli "twin," Qâyeni jamal "twin," Tabari da-cembali "twin;" PIE base *iem- "to hold."

Dopeykar, from do "two" (Mid.Pers. do, Av. dva-; Skt. dvi-; Gk. duo; L. duo ( Fr. deux); E. two; Ger. zwei) + peykar "figure, form, body" (from Mid.Pers. pahikar "picture, image;" from O.Pers. patikara- "picture, (sculpted) likeness," from patiy "against" (Av. paiti; Skt. prati; Gk. poti/proti) + kara- "doer, maker," from kar- "to do, make, build;" Av. kar-; Skr. kr-; cf. Skt. pratikrti- "an image, likeness, model; counterpart").

A → meteor shower that occurs in the first half of December, with its → radiant in the → constellation → Gemini. Geminids are pieces of debris from the extinct comet → 3200 Phaethon. The shower appears when Earth runs into a stream of the debris every year in mid-December, causing → meteors to fly from that constellation.

→ Gemini + → -ids.

The brightest star in the constellation → Corona Borealis. Same as → Alphekka.

Gemma, from L. gemma "precious stone, jewel," originally "bud," from the root *gen- "to produce", → generate.

Alfakké, → Alphekka.

In some languages (not in English, nor in Persian) a set of two or more grammatical categories (called → masculine, → feminine, and → neuter) into which nouns, pronouns, and adjectives are divided. For example, French, Spanish, and Italian have two genders, masculine and feminine (shown, for example, in French by the use of le and la, respectively); German and Russian have three genders, masculine, feminine, and neuter. Ancient Iranian languages had three genders, like Sanskrit and Greek.

From M.E. gendre, from O.Fr. gendre, from stem of L. genus "race, stock, family; kind, rank, order; species."

Žâné "race, species," ultimately from Proto-Ir. *zan- "to be born," cf. Av. za(n)- "to give birth; to be born;" related to Pers. zâdan, akin to L. genus, as above, → generate; the transformation of z into ž, as in nežâd, → race.

The basic unit of hereditary that is an ordered sequence of nucleotides located in a particular position of a particular chromosome. It is the means by which characteristics are transmitted from parents to offsprings.

From Ger. Gen, coined 1905 by Danish scientist Wilhelm Ludvig Johannsen (1857-1927), from Gk. genos "race, kind," genesis "origin," genea "generation, race;" cognate with L. genus "race, stock;" generare "to bring forth;" Pers. zâdan "to bring forth;" → generate.

Žen, loanword from Fr., as above.

(Adj.) 1) Not limited to one class, field, product, service, etc. 2) Relating to the whole or to the all or most. 3) Dealing with overall characteristics, universal aspects, or important elements.
See also:
→ general precession, → general relativity, → generalization, → generalize, → generalized, → generalized coordinates, → generalized forces, → generalized momenta, → generalized velocities, → New General Catalogue (NGC).

From L. generalis "relating to all, of a whole class," from genus "race, stock, kind," akin to Pers. zâdan, Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" Mod.Pers. zâdan, present stem zā- "to bring forth, give birth" (Mid.Pers. zâtan; cf. Skt. jan- "to produce, create; to be born," janati "begets, bears;" Gk. gignomai "to happen, become, be born;" L. gignere "to beget;" PIE base *gen- "to give birth, beget."

Harvin, from Mid.Pers. harvin "all," from har(v) "all, each, every" (Mod.Pers. har "every, all, each, any"); O.Pers. haruva- "whole, all together;" Av. hauruua- "whole, at all, undamaged;" cf. Skt. sárva- "whole, all, every, undivided;" Gk. holos "whole, complete;" L. salvus "whole, safe, healthy," sollus "whole, entire, unbroken;" PIE base *sol- "whole."

The secular motions of the → celestial equator and → ecliptic. In other words, the sum of → lunisolar precession, → planetary precession, and → geodesic precession.

→ general; → precession

The secular displacement of the → equinox on the → ecliptic of date.

→ general; → precession; → longitude.

The secular motion of the → equinox along the → celestial equator.

→ general; → precession; → right ascension.

Of, relating to, or subject to the theory of → general relativity.

→ general; → relativistic.

The theory of → gravitation developed by Albert Einstein (1916) that describes the gravitation as the → space-time curvature caused by the presence of matter or energy. Mass creates a → gravitational field which distorts the space and changes the flow of time. In other words, mass causes a deviation of the → metric of space-time continuum from that of the "flat" space-time structure described by the → Euclidean geometry and treated in → special relativity. General relativity developed from the → principle of equivalence between gravitational and inertial forces. According to general relativity, photons follow a curved path in a gravitational field. This prediction was confirmed by the measurements of star positions near the solar limb during the total eclipse of 1919. The same effect is seen in the delay of radio signals coming from distant space probes when grazing the Sun's surface. Moreover, the space curvature caused by the Sun makes the → perihelion of Mercury's orbit advance by 43'' per century more than that predicted by Newton's theory of gravitation. The → perihelion advance can reach several degrees per year for → binary pulsar orbits. Another effect predicted by general relativity is the → gravitational reddening. This effect is verified in the → redshift of spectral lines in the solar spectrum and, even more obviously, in → white dwarfs. Other predictions of the theory include → gravitational lensing, → gravitational waves, and the invariance of Newton's → gravitational constant.

→ general; → relativity.

→ secretary-general.

→ general; → secretary.

The act or process of generalizing; → generalize.
A result of this process; a general statement, proposition, or principle.

Verbal noun of → generalize.

To make general, to include under a general term; to reduce to a general form.
To infer or form a general principle, opinion, conclusion, etc. from only a few facts, examples, or the like.

→ general; → -ize.

Made general. → generalized coordinates; → generalized velocities.

P.p. of → generalize