greatest eastern elongation
bozorgtarin derâzeš-e xâvari
Fr.: plus grande élongation est
The Greatest → elongation of an inferior planet occurring after sunset.
Fr.: la plus grande éclipse
The instant when the axis of the Moon's → shadow cone passes closest to Earth's center. For → total eclipses, the instant of greatest eclipse is virtually identical to the instants of greatest magnitude and greatest duration. However, for → annular eclipses, the instant of greatest duration may occur at either the time of greatest eclipse or near the sunrise and sunset points of the eclipse path (F. Espenak, NASA).
greatest western elongation
bozorgtarin derâzeš-e bâxtari
Fr.: plus grande élongation ouest
The Greatest → elongation of an inferior planet occurring before sunrise.
Greek numeral system
râžmân-e adadhâ-ye Yunâni
Fr.: numération grecque
A → numeral system in which letters represent numbers. In an earlier system, called acrophonic, the symbols for numerals came from the first letter of the number name. Subsequently, the numerals were based on giving values to the letters of alphabet. For example α, β, γ, and δ represented 1, 2, 3, and 4; while ι, κ, λ, and μ stood for 10, 20, 30, and 40, and ρ, σ, τ, and υ for 100, 200, 300, and 400. The Greek also used the additive principle. For example 11, 12, 13, 14, and 374 were written ια, ιβ, ιγ, ιδ, and τοδ. The numbers between 1000 and 9000 were expressed by adding a subscript or superscript ι (iota) to the symbols for 1 to 9. For example ιA and ιΘ for 1000 and 9000. Numbers greater than 9999 were expressed using M, which was the myriad, 10,000. Therefore, since 123 was represented by ρκγ, 123,000 was written as Mρκγ.
A color intermediate in the spectrum between yellow and blue (wavelength between 5000 and 5700 Å). The color of most grasses and leaves while growing.
Green, from O.E. grene, related to growan "to grow," from W.Gmc. *gronja- (cf. Dan. grøn, Du. groen, Ger. grün), from PIE base *gro- "to grow."
Sabz "green," from Mid.Pers. sabz "green, fresh," related to sabzi "grass."
deraxš-e sabz (#)
Fr.: rayon vert
A brilliant green color that occasionally appears on the upper limb of the Sun as it rises or sets.
green pea galaxy
kahkešân-e noxod sabz
Fr.: galaxie petit pois
A member of a class of galaxies of relatively small size having very strong emission lines especially [O iii] 5007 Å and an unusually large → equivalent width of up to 1000 Å. They were first noted because of their peculiar bright green color and small size, unresolved in Sloan Digital Sky Survey imaging. Most of the green pea galaxies are low-mass galaxies (M ~ 108.5 to 1010→ solar masses), with high → star formation rates (~ 10 solar masses per year), solar → metallicities, and → redshifts ranging from z = 0.112 to 0.360 (See Cardamone et al. 2009, MNRAS 399, 1191; Izotov et al. 2010, astro-ph/1012.5639).
A building with transparent walls and roof, usually of glass, for the cultivation and exhibition of plants under controlled conditions (Dictionary.com).
Fr.: effet de serre
An increase in → temperature caused when incoming → solar radiation is passed but outgoing → thermal radiation is trapped by the → atmosphere. The major factors for this effect are → carbon dioxide and → water vapor. The greenhouse effect is very important on Venus and Earth but very weak on Mars. On average, about one third of the solar radiation that hits the Earth is reflected back to space. The Earth's surface becomes warm and emits → infrared radiation. The → greenhouse gases trap the infrared radiation, thus warming the atmosphere. Without the greenhouse effect the Earth's average global temperature would be -18° Celsius, rather than the present 15° Celsius. However, human activities are causing greenhouse gas levels in the atmosphere to increase.
gâzhâ-ye dârâ-ye oskar-e garmxâné
Fr.: gaz à effet de serre
Gases responsible for the greenhouse effect. These gases include: water vapor (H2O), carbon dioxide (CO2); methane (CH4); nitrous oxide (N2O); chlorofluorocarbons (CFxClx); and tropospheric ozone (O3).
Greenwich Apparent Sidereal Time (GAST)
zamân-e axtari-ye padidâr-e Greenwich
Fr.: temps sidéral apparent de Greenwich
Greenwich Mean Sidereal Time (GMST)
zamân-e axtari-ye miyângin-e Greenwich
Fr.: temps sidéral moyen de Greenwich
Fr.: méridien de Greenwich
A borough in southeast London, England, on the Thames River. It is the site of the original Royal Observatory, through which passes the prime meridian, or longitude 0°; → meridian.
Greenwich sidereal date
ruz-e axtari-ye Greenwich
Fr.: jour sidéeal de Greenwich
Greenwich sidereal day number
šomâre-ye ruz-e axtari-ye Greenwich
Fr.: nombre du jour sidéral de Greenwich
The integral part of the → Greenwich sidereal date.
gâhšomâr-e Gregori (#)
Fr.: calendrier grégorien
A → solar calendar in which the year length is assumed to be 365.2425 solar days. It is now used as the civil calendar in most countries. The Gregorian calendar is a revision of the → Julian calendar instituted in a papal bull by Pope Gregory XIII in 1582. The reason for the calendar change was to correct for drift in the dates of significant religious observations (primarily Easter) and to prevent further drift in the dates.
Named after Pope Gregory XIII (1502-1585), an Italian, born Ugo Boncompagni, Pope from 1572 to 1585, who ordered the reform of the Julian calendar; → calendar.
durbin-e Gregori, teleskop-e ~ (#)
Fr.: télescope de Gregory
A reflecting telescope in which the light rays are reflected from the primary mirror to a concave secondary mirror, from which the light is reflected back to the primary mirror and through the central hole behind the primary mirror. Compare with the → Cassegrain telescope, in which the secondary mirror is convex.
Named after the Scottish mathematician and astronomer James Gregory (1638-1675), who devised the telescope, but did not succeed in constructing it; → telescope.
Greisen-Zatsepin-Kuzmin limit (GZK)
Fr.: limite de Greisen-Zatsepin-Kuzmin
A theoretical limit of approximately 6 × 1019 → electron-volts for the energy of → cosmic rays above which they would lose energy in their interaction with the → cosmic microwave radiation background photons. Cosmic ray protons with these energies produce → pions on blackbody photons via the Δ resonance according to: γCMB + p → p + π0, or γCMB + p → n + π+, thereby losing a large fraction of their energy. These interactions would reduce the energy of the cosmic rays to below the GZK limit. Due to this phenomenon, → Ultra-high-energy cosmic rays are absorbed within about 50 Mpc.
Named after Kenneth Greisen (1966), Physical Review Letters 16, 748 and Georgiy Zatsepin & Vadim Kuzmin (1966), Journal of Experimental and Theoretical Physics Letters 4, 78; → limit.
1) A → grating of crossed bars; gridiron.
Shortening of gridiron "a utensil consisting of parallel metal bars on which to broil meat or other food," from M.E. griderne, from gridel, from O.Fr. gredil, gridil, from L. craticula "gridiron, small griddle," diminutive of cratis "wickerwork."
Šabâk, from Laki šowâk "a net woven from goat fleece used for carrying chaff or fruits like melon," variants šâvâk (Lori), šavak (Nahâvand).