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

Of or pertaining to the force produced by the rotation of the Earth.

From Gk. → geo- + Gk. strophe "a turning," from strephein "to turn," from PIE *strebh- "to wind, turn" + → -ic.

From zamin-, → geo-, + carxeši, → rotational.

Meteo.: The balance between the → Coriolis force and the → pressure gradient force. See also → geostrophic flow.

→ geostrophic; → balance.

Oceanography: A flow resulting from → geostrophic balance. In geostrophic flow water moves along the lines of constant pressure or → isobars. Geostrophic flow is characterized by small → Rossby and → Ekman numbers.

→ geostrophic; → flow.

Meteo.: A wind which is balanced by the → Coriolis effect and → pressure gradient force. An air parcel initially at rest will move from high pressure to low pressure because of the pressure gradient force. However, the air parcel in its movement is deflected by the Coriolis force, to the right in the northern hemisphere and to the left on the southern hemisphere. As the wind gains speed, the deflection increases until the Coriolis force equals the pressure gradient force. At this point, the wind will be blowing parallel to the → isobars.

→ geostrophic; → wind.

A circular orbit around the Earth identical to a geostationary orbit except that the satellite's orbit does not necessarily lie in the Earth's equatorial plane.

→ geo-; → synchronous; → orbit.

An equatorial mounting in which the declination axis is at the end of the polar axis, which is on top of a pier to raise the telescope to a convenient height.

German, from L. Germanus, maybe of Gaulish (Celtic) origin, perhaps originally meaning "noisy" (cf. O.Ir. garim "to shout") or "neighbor" (cf. O.Ir. gair "neighbor"); → mounting.

Barnešând, → mounting; Âlmâni "German," from Âlmân, from Fr. Allemand "German," from P.Gmc. *Alamanniz, probably meaning "all-man" and denoting a wide alliance of tribes. Alternatively, perhaps meaning "foreign men," cognate with L. alius "the other."

A noun formed from a verb, denoting an action or state. In English, the gerund is the "-ing" form of a verb when it functions grammatically as a noun in a sentence; it is identical in appearance to the present participle.

From L.L. gerundium, from gerundum "to be carried out," gerundive of gerere "to bear, carry."

Karnâm, short for karvâznâm, from karvâz, → verb, + nâm "name, → noun."

Giga (billion) → electron volt. A unit of → energy used to describe the total energy carried by a → particle or → photon.

→ giga- + → electron volt.

A faint false image caused by reflection that is sometimes seen in an optical system. In spectroscopy, a false image of a spectral line formed by irregularities in the ruling of diffraction gratings.

Ghost, from O.E. gast "soul, spirit, breath," from P.Gmc. *ghoizdoz (cf. M.Du. gheest, Ger. Geist "spirit, ghost"), from PIE base *ghois- "to be excited, frightened;" cf. Av. zaēša- "horrible, frightful," zôiždišta- "the most loathsome;" Mid./Mod.Pers. zešt "ugly, disgusting;" Goth. usgaisjan "to be afraid;" O.E. gæstan "to frighten."

Parhib "ghost," Pers. word of Xorâsâni dialect.

A star forming region in the → Large Magellanic Cloud, a satellite of our Galaxy, as pictured by the → Hubble Space Telescope. It spans about 50 light-years and contains several young, → massive stars.

→ ghost; → head; → nebula

A person or thing of unusually great size, power, importance. In astronomy, e.g. → giant star, → giant branch, → red giant.

From O.Fr. géant, from V.L. *gagantem, from L. gigas "giant," from Gk. gigas (gen. gigantos), huge and savage monsters, children of Gaia and Uranus, who fought the Olympians but were eventually destroyed by the gods, probably from a pre-Gk. language. The Gk. word was used in Septuagint (the Greek translation of the Jewish Scriptures) to refer to men of great size and strength, hence the expanded use in Western languages.

Qul "an imaginary hideous demon, supposed to devour men and animals," Pers. word probably related to Skt. grábha- "a demon causing diseases, one who seizes," grahila- "possessed by a demon," from grah-, grabh- "to seize, take," graha "seizing, holding, perceiving," Av./O.Pers. grab- "to take, seize;" Mid.Pers. griftan; Mod.Pers. gereftan "to take, seize;" cf. M.L.G. grabben "to grab," from P.Gmc. *grab, E. grab "to take or grasp suddenly;" PIE base *ghrebh- "to seize."
Qulpeykar, from qul, as explained, + 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-; Skt. kr-; cf. Skt. pratikrti- "an image, likeness, model; counterpart").
Kalân "great, large, big, bulky."

A conspicuous family of stars in the → Hertzsprung-Russell diagram composed of red, evolved stars with large sizes. → giant star; → red giant.

→ giant; → branch.

An → H II region emitting at least 10⁵⁰ → Lyman continuum photons per second, or about 10 times → Orion nebula. Such an H II region should be powered by at least one O3V star or by at least a dozen → O-type and tens → B-type stars. Our nearest giant H II region is → NGC 3603. Some other Galactic giant H II regions are: → Lagoon Nebula, M17, W31, W51A, and NGC 3576.

→ giant; → H II; → region.

A quantum mechanical phenomenon where the resistance of certain materials drops dramatically upon application of a magnetic field in certain structures composed of alternating layers of magnetic and nonmagnetic metals. The basis of the GMR is the dependence of the electrical resistivity of electrons in a magnetic metal on the direction of the electron spin, either parallel or anti-parallel to the magnetic moment of the layers. The 2007 Nobel Prize in physics was awarded to the French physicist Albert Fert (1938-) and German physicist Peter Grünberg (1939-) for the discovery of GMR.

→ giant; magneto- combining form of → magnet; → resistance.

A massive complex of → interstellar gas and → dust, consisting mostly of → molecular hydrogen, that typically stretches over 150 light-years and contains several hundred thousand → solar masses. Giant molecular clouds are the principal sites of star formation. → molecular cloud.

→ giant; → molecular; → cloud.

A planet much more massive than Earth. The solar system has four giant planets: → Jupiter, → Saturn, → Uranus, and → Neptune.

→ giant; → planet.

A high-luminosity star that has evolved off the → main sequence and lies above the main sequence on the → Hertzsprung-Russell diagram. A member of the → giant branch. → red giant.

→ giant; → planet.

An adjective applied to the phase of the Moon (or a planet) when it is more than half full, but less than entirely full.

From L.L. gibbous "hunchbacked," from L. gibbus "hump, hunch;" cf. Mod.Pers. kaž "crooked, bent, being aside;" Skt. kubja- "hump-backed, crooked;" Pali kujja- "bent;" Lith. kupra "hump."

Kuž "humped," Mid.Pers. kôf "hill, mountain; hump" (Mod.Pers. kuh, "mountain"), kôfik "humpbacked," O.Pers. kaufa-, Av. kaofa- "mountain;" mâh, → moon.

The probability distribution of the various possible states of a certain → quasi-closed subsystem.

→ Gibbs free energy; → canonical; → distribution.

The total energy needed to create a thermodynamic system minus the energy provided the environment. It is defined by G = U + PV -TS, where U is the → internal energy, T the → absolute temperature, S the → entropy, P the → pressure, and V is the final → volume. Same as the → Gibbs function and → thermodynamic potential.

Named after Josiah Willard Gibbs (1839-1903), an American physicist who played an important part in the foundation of analytical thermodynamics; → free; → energy.