<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir cla clo clo clu coa coe coh col col col com com com com com com com com com con con con con con con con con con con con coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat Ré rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>
Barycentric Dynamical Time (TDB) zamân-e tavânik-e gerânigâhi Fr.: temps dynamique barycentrique (TDB) A time scale previously used in calculations of the orbits of solar system objects (planets, asteroids, comets, and interplanetary spacecrafts). It was based on the Terrestrial Dynamical Time, but took the relativistic effect of time dilation into account to move the origin to the solar system barycenter. It is now superseded by → Barycentric Coordinate Time (TCB). → barycenter; → dynamical; → time. |
Barycentric Julian Date (BJD) gâhdâd-e žulian-e gerânigâhi Fr.: date julienne barycentrique The → Julian Date referenced to the → barycenter of the → solar system. The BJD is more precise than the → Heliocentric Julian Day because the Sun is not stationary. It moves due to the → gravitational attraction of Jupiter and the other planets. → barycentric; → Julian Date. |
baryogenesis bâriyonzâyi Fr.: baryogénèse The hypothetical mechanism of creating the → baryon asymmetry in the → Universe. Universe. Explaining the observed matter asymmetry is an important open question in physical cosmology. → Sakharov conditions. |
baryon bâriyon (#) Fr.: baryon Any of the class of the heaviest → subatomic particles that includes → protons, → neutrons, as well as a number of short-lived particles whose decay products include protons. Baryons obey the → Fermi-Dirac statistics. They form a subclass of the → hadrons and are further subdivided into → nucleons and → hyperons. Gk. barys "heavy" + → -on, from "fermion." |
baryon acoustic oscillation (BAO) naveš-e sedâyik-e bâryoni Fr.: oscillation acoustique baryonique In cosmology, one of a series of peaks and troughs that are present in the power spectrum of matter fluctuations after the → recombination era, and on large scales. At the time of the Big Bang, and for about 380,000 years afterwards, Universe was ionized and photons and baryons were tightly coupled. Acoustic oscillations arose from perturbations in the primordial plasma due to the competition between gravitational attraction and gas+photons pressure. After the epoch of recombination, these oscillations froze and imprinted their signatures in both the → CMB and matter distribution. In the case of the photons, the acoustic mode history is manifested as the high-contrast Doppler peaks in the temperature anisotropies. As for baryons, they were in a similar state, and when mixed with the non-oscillating → cold dark matter perturbations, they left a small residual imprint in the clustering of matter on very large scales, ~100 h^{-1}Mpc (h being the → Hubble constant in units of 100 km s^{-1} Mpc^{-1}). The phenomenon of BAOs, recently discovered using the Sloan Digital Sky Survey data, is a confirmation of the current model of cosmology. Like → Type Ia supernovae, BAOs provide a → standard candle for determining cosmic distances. The measurement of BAOs is therefore a powerful new technique for probing how → dark energy has affected the expansion of the Universe (see, e.g., Eisenstein 2005, New Astronomy Reviews 49, 360; Percival et al. 2010, MNRAS 401, 2148). → baryon; → acoustic; → oscillation. |
baryon asymmetry nâhamâmuni-ye bariyon Fr.: asymmétrie baryonique The observation that in the present → Universe there is → matter but not much → antimatter. Observations do not show the presence of galaxies made of antimatter, nor gamma rays are observed that would be produced if large entities of antimatter would undergo → annihilation with matter. However, the → early Universe could have been baryon symmetric, and for some reason the matter excess has been generated, through some process called → baryogenesis. → Sakharov conditions. |
baryon number adad-e bâriyoni (#) Fr.: nombre baryonique 1) The difference between the total number of → baryons and
the total number of → antibaryons in a system of
→ subatomic particles.
It is a measure of → baryon asymmetry and is
defined by the quantity
η = (n_{b} - n_{b-})/n_{γ},
called the → baryon-photon ratio,
where n_{b} is the → comoving number
density of baryons, n_{b-} is the number of
antibaryons, and n_{γ} is that of photons. The value of η for
the → cosmic microwave background radiation (CMBR)
has been very well determined by the → WMAP satellite to be
η = (6.14 ± 0.25) x 10^{-10}. The baryon number is assumed to be
constant. The photons created in
stars amount to only a small fraction, less than 1%, of those in the CMBR. |
baryon-photon ratio vâbar-e bâriyon-foton Fr.: rapport baryon-photon The → baryon number compared with the number of photons in the → Universe. The baryon-photon ratio can be estimated in a simple way. The → energy density associated with → blackbody radiation of → temperature T is aT^{4}, and the mean energy per photon is ~kT. Therefore, the number density of blackbody photons for T = 2.7 K is: n_{γ} = aT^{4}/kT = 3.7 x 10^{2} photons cm^{-3}, where a = 7.6 x 10^{-15} erg cm^{-3} K^{-4} (→ radiation density constant) and k = 1.38 x 10^{-16} erg K^{-1} (→ Boltzmann's constant). The number density of baryons can be expressed by ρ_{m}/m_{p}, where ρ_{m} is the mass density of the Universe and m_{p} is the mass of the → proton (1.66 x 10^{-24} g). → CMB measurements show that the baryonic mean density is ρ_{m} = 4.2 x 10^{-31} g cm^{-3} (roughly 5% of the → critical density). This leads to the value of ~ 2 x 10^{-7} for the number density of baryons. Thus, the baryon/photon ratio is approximately equal to η = n_{b}/n_{γ} = 2 x 10^{-7}/3.7 x 10^{2} ~ 5 x 10^{-10}. In other words, for each baryon in the Universe there is 10^{10} photons. This estimate is in agreement with the precise value of the baryon-photon ratio 6.14 x 10^{-10} derived with the → WMAP. Since the photon number and the baryon number are conserved, the baryon-photon ratio stays constant as the Universe expands. |
baryonic dark matter mâde-ye siyâh-e bâriyoni Fr.: matière noire baryonique → Dark matter made up of → baryons that are not luminous enough to produce any detectable radiation. It is generally believed that most dark matter is → non-baryonic. The baryonic dark matter could reside in a number of forms, including cold gas and compact objects. |
baryonic matter mâde-ye bâriyoni (#) Fr.: matière baryonique Ordinary matter composed of → baryons, i.e. → protons and → neutrons, as distinct from → non-baryonic, exotic forms. |
basalt bâzâlt (#) Fr.: basalte A dark fine-grained → igneous rock typically composed of → plagioclase with → pyroxene and → olivine and often displaying a columnar structure. From L.L. basaltes, misspelling of L. basanites "very hard stone," from Gk. basanites, from basanos "touchstone," from Egyptian baban "a stone used by the Egyptians as a touchstone of gold." |
base 1, 2, 3, 4) pâyé (#), 5) pâygâh (#), 6) bâz (#) Fr.: base 1) The bottom support of anything; a fundamental principle or groundwork. M.E., from O.Fr. bas, from L. basis "foundation," from Gk. basis "step, pedestal," from bainein "to step." Pâyé "base," from pâ, pây "foot," from Mid.Pers. pâd, pây;
Av. pad-, cf. Skt. pat: Gk. pos, genitive podos;
L. pes; PIE *pod-/*ped-. |
baseline pâye-xatt Fr.: ligne de base 1) In radio interferometry, the separation between the electrical,
or phase centers of two interferometer elements. |
basic bâzi (#) Fr.: basique Chemistry: Of or denoting or of the nature of or containing a → base. Same as → alkaline. |
basin howzé (#) Fr.: bassin A large impact crater on a planet or moon, typically several hundred kilometers across, flooded with basaltic lava and surrounded by concentric rings of faulted cliffs. From O.Fr. bacin, from V.L. *baccinum, from L. bacca "water vessel," perhaps originally Gaulish. Howzé, from howz "pond, a large reservoir of water" (from Ar. hauz) + -é noun suffix. |
battery bâtri (#) Fr.: batterie A combination of → cells connected together so as to produce useful electrical energy. M.Fr. batterie "a grouping of artillery pieces for tactical purposes," from O.Fr. baterie "beatng, thrashing, assault," from battre "to beat," from L. battuere "to beat." Bâtri, loanword from Fr., as above. |
bay bâhé Fr.: baie A body of water forming an indentation of the shoreline, larger than a cove but smaller than a → gulf (Dictionary.com). M.E. baye, from M.Fr. baie, from L.L. bâia, perhaps ultimately from Iberian bahia. Bâhé, loan from Sp. bahia. |
Bayer designation nâmgozini-ye bayer Fr.: designation de Bayer A stellar designation system in which a specific star is identified by a Greek letter, followed by the genitive form of its hosting → constellation's Latin name. For example, Alpha Eridani, Delta Cephei, Lambda Bootis. The Greek alphabet has only 24 letters. In case a single constellation contained a larger number of stars, Bayer amended with Latin letters: upper case A, followed by lower case b through z (omitting j and v), for a total of another 24 letters. Bayer did not go beyond z, but later astronomers added more designations using both upper and lower case Latin letters, the upper case letters following the lower case ones in general. Examples include, for Vela: a Vel (Velorum), z Vel, A Vel, Q Vel; for Scorpius: d Sco (Scorpii), A Sco; for Leo: b Leo (Leonis), o Leo, A Leo, → c Orionis. Compare with the → Flamsteed designation. First introduced by Johann Bayer (1572-1625) in his atlas Uranometria, published in 1603 at Augsburg, Germany; → designation. |
Bayes' theorem farbin-e Bayes Fr.: théorème de Bayes A theorem in probability theory concerned with determining the → conditional probability of an event when another event has occurred. Bayes' theorem allows revision of the original probability with new information. Its simplest form is: P(A|B) = P(B|A) P(A)/P(B), where P(A): independent probability of A, also called prior probability; P(B): independent probability of B; P(B|A): conditional probability of B given A has occurred; P(A|B): conditional probability of A given B has occurred, also called posterior probability. Same as Bayes' rule. Named after its proponent, the British mathematician Reverend Thomas Bayes (1702-1761). However, Bayes did not publish the theorem during his lifetime; instead, it was presented two years after his death to the Royal Society of London. |
Bayesian Bayesi Fr.: bayésien Being, relating to, or denoting statistical methods based on → Bayes' theorem. Referring to → Bayes' theorem. |
<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir cla clo clo clu coa coe coh col col col com com com com com com com com com con con con con con con con con con con con coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat Ré rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>