Fr.: paramètre de Fried
One of the parameters that characterize atmospheric → seeing. It is the diameter of the largest aperture that can be used before → turbulence starts to degrade the image quality. As the turbulence gets stronger, the Fried parameter, denoted r0, becomes smaller. The Fried parameter is wavelength dependent: r0 ∝ λ6/5. On best astronomical mountain tops it ranges between 20 and 30 cm for λ = 5000 A.
Named after David L. Fried, who defined the parameter 10 1966; → parameter.
Fr.: équation de Friedmann
An equation that expresses energy conservation in an → expanding Universe. It is formally derived from → Einstein's field equations of → general relativity by requiring the Universe to be everywhere → homogeneous and → isotropic. It is expressed by H2(t) = (8πG)/(3c2)ε(t) - (kc2)/R2(t), where H(t) is the → Hubble parameter, G is the → gravitational constant, c is the → speed of light, ε(t) is the → energy density, k is the → curvature of space-time, and R(t) is the → cosmic scale factor. See also → Big Bang, → accelerating Universe. See also → Friedmann-Lemaitre Universe.
Named after the Russian mathematician and physical scientist Aleksandr Aleksandrovich Friedmann (1888-1925), who was the first to formulate an → expanding Universe based on Einstein's theory of → general relativity ; → equation.
Fr.: univers Friedmann-Lemaître
Fr.: glacial, froid, glacé, frigide
Very cold in temperature.
From Latin frigidus "cold, chill, cool," from stem of frigere "be cold;" related to noun frigus "cold, coldness, frost," from PIE root *srig- "cold;" cf. Gk. rhigos "cold, frost."
Sajan "very cold," variants šaja,, sajâm, šajad, Oss. I. syjyn/syd, D. sujun/sud "to freeze," Yaghnobi ši-, Yazghulami šed/šiy- "to freeze," Shughni šitô , Sariqoli š(i)tu "cold, ice." Proto-Ir. *saiH-/siH- "to freeze." Skt. syā- "to freeze, coagulate, become rigid."
1) One of the alternating bright or dark bands produced by
→ interference or → diffraction.
From M.E. frenge, from O.Fr. frange, from V.L. *frimbia, metathesis of L. fimbriæ "fibers, threads, fringe," of uncertain origin.
Fariz, contraction of farâviz "fringe, lace, edging," from far-, par-, variant pirâ- "around, about" (Mid.Pers. pêrâ; O.Pers. pariy "around, about," Av. pairi "around, over;" Skt. pari; Indo-Iranian *pari- "around;" PIE base *per- "through, across, beyond;" cf. Gk. peri "around, about, beyond;" L. per "through") + âviz "anything suspended; a place where things are hung up; a border, margin," from âvixtan, âvizidan "to hang, suspend;" Mid.Pers. âwextan "to hang;" Av. vij- "to shake, swing," frauuaēγa- "swinging forward;" cf. Skt. vej- "to dart up or back, move up;" Proto-Iranian *uij- "to shake, swing."
A tailless amphibian with a short squat body, moist smooth skin, a large head, and very long hind legs for leaping.
Qurbâqe "frog," prefixed bâq, variants Tabari, Aftari vak, Tabari vag, Lori, Laki qorvâ, korvâx, Kurd. baq, Zâzâ baqa; Mid.Pers. vazak, vak; Av. vazaγa- "frog."
Fr.: face, front
1) The part or side of anything that faces forward.
→ ionization front.
From O.Fr. front "forehead, brow," from L. frontem "forehead," perhaps lit. "that which projects," from PIE *bhront-, from base *bhren- "to project, stand out."
Pišân, from pišâni "front, forehead," from piš
"before; in front," from Mid.Pers. pêš "before, earlier;"
O.Pers. paišiya "before; in the presence of" + -ân suffix
of place and time.
A device containing a radio-frequency amplifier and associated cryogenic systems, routers, and converters (mixers), whose input is the voltage from a receptor and whose output is an intermediate-frequency signal. → back-end.
→ front + end, from O.E. ende, from P.Gmc. *andja, originally "the opposite side," from PIE *antjo "end, boundary," from base *anta-/*anti- "opposite, in front of, before."
Piš-tah, from piš, → front, + tah "end;" Mid.Pers. tah "bottom." The origin of this term is not clear. It may be related to Gk. tenagos "bottom, swamp," Latvian tigas "depth;" PIE *tenegos "water bottom."
A border between two countries.
From O.Fr. fronter, from front "forehead, brow," → front.
Marz, from Mid.Pers. marz "boundary;" Av. marəza- "border, district," marəz- "to rub, wipe;" Mod.Pers. parmâs "contact, touching" (→ contact), mâl-, mâlidan "to rub;" PIE base *merg- "boundary, border;" cf. L. margo "edge" (Fr. marge "margin"); P.Gmc. *marko; Ger. Mark; E. mark, margin.
Fr.: Champs frontialers
An observing project using the → Hubble Space Telescope (HST) and the → Spitzer Space Telescope to obtain deep images for cosmological studies. The Frontier Fields combines the power of HST and Spitzer with the natural gravitational telescopes of massive high-magnification clusters of galaxies to produce the deepest observations of clusters and their lensed galaxies ever obtained. Six clusters (Abell 2744, MACSJ0416.1-2403, MACSJ0717.5+3745, MACSJ1149.5+2223, Abell S1063, and Abell 370) were selected based on their lensing strength, sky darkness, Galactic extinction, parallel field suitability, accessibility to ground-based facilities, HST, Spitzer and JWST observability, and preexisting ancillary data. (Lotz et al., 2016, arxiv/1605.06567 and references therein).
Fr.: givre, gelée
Ice crystals that are formed by deposition of water vapor on a relatively cold surface.
O.E. forst, frost "a freezing, becoming frozen, extreme cold," from P.Gmc. *frusta- (cf. O.H.G. frost, Du. vorst), related to freosan "to freeze."
Bašmé, from bašm "hoar-frost; dew," variants bažm, bašk, pašak "frost; dew," may be related to (Âštiyâni, Qomi dialects) bašand, vašand, vašan "rain" (vašan-sâl "rainy year"), (Lori, Laki) vašt "rain shower," (Gurâni) wašt, wišani "rain" (Tâti Karingâni) vurasten "to rain;" Av. -varšta- "rain," aiwi-varšta- "rained upon;" Skt. vars- "to rain," varsá- "rain;" M.Irish frass "rain shower, torrent;" Gk. eérse "dew," oureo "to urinate."
Fr.: nombre de Froude
A → dimensionless number that gives the ratio of local acceleration to gravitational acceleration in the vertical.
Named after William Froude (1810-1879), English engineer.
yax basté, rocidé
Past participle of → freeze.
frozen magnetic field line
xatt-e meydân-e meqnâtisi-ye yax basté, ~ ~ ~ rocidé
Fr.: ligne de champ magnétique gelée
âb-e yax basté, âb-e rocidé
Fr.: eau gelée
Past participle of → freeze.
FU Orionis object
barâxt-e FU Šekârgar
Fr.: objet FU Orionis
A member of a class of → pre-main sequence stars that experience dramatic changes in magnitude and → spectral type. During an outburst the luminosity of such an object can increase by several orders of magnitude on short time-scales (few months to few years). The phenomenon is explained by abrupt mass transfer from an → accretion disk to a young, low mass → T Tauri star (accretion rates 10-4 to 10-3 solar masses per year). → EX Lupi; → Z CMa.
Completely filled; containing all that can be held; complete; entire; maximum.
O.E. full "completely, full," from P.Gmc. *fullaz (cf. O.Fris. ful, O.N. fullr, O.H.G. fol, Ger. voll), akin to Pers. por, as below.
Por "full;" Mid.Pers. purr "full;" O.Pers. paru- "much, many;" Av. parav-, pauru-, pouru-, from par- "to fill;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.
full micro Moon
riz pormâng, ~ pormâh
Fr.: pleine lune d'apogée
Same as → apogee full Moon.
pormâng, pormâh (#)
Fr.: pleine lune
1) The moon at → opposition, when it appears as a round disk
to an observer on the Earth because the illuminated side is toward him.
full super Moon
abar pormâng, abar pormâh
Fr.: pleine lune de périgée
Same as → perigee full Moon.