An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian
فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک
M. Heydari-Malayeri - Paris Observatory
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daylight saving time vaxt-e nur anduzi, vaqt-e ~ Fr.: heure d'été A system of adjusting the official local time in some countries in order to provide a better match between the hours of daylight and the active hours of work and school. The "saved" daylight is spent on evening activities which get more daylight, rather than being "wasted" while people sleep past dawn. Although known also as summer time, it includes the spring season and nearly half of autumn. → day; → light; saving, from save, from O.Fr. sauver, from L.L. salvare "to secure," from L. salvus "safe," PIE *solwos, from base *sol- "whole" (cf. O.Pers. haruva-, Av. haurva- "whole, intact," Mod.Pers. har "every, all; any," Skt. sarva- "whole, entire," Gk. holos "whole"); → time. Vaxt, written vaqt |
daytime ruzhangâm (#) Fr.: temps de jour The time interval when the Sun is above the horizon for a given position. Ruzhangâm, from ruz→ day + hangâm "time, hour, season," Mid.Pers. hangâm "time, epoch, season," Av. ham-gam- "to meet together," from ham- "together," → com- + gam- "to come; to go," jamaiti "goes," O.Pers. gam- "to come; to go," Mod.Pers. âmadan "to come," Skt. gamati "goes," Gk. bainein "to go, walk, step," L. venire "to come," Tocharian A käm- "to come," O.H.G. queman "to come," E. come; PIE root *gwem- "to go, come." |
DB white dwarf sefid kutule-ye DB Fr.: naine blanche DB A → white dwarf whose spectrum shows strong He I in the absence of hydrogen or metal lines. |
DC white dwarf sefid kutule-ye DC Fr.: naine blanche DC A → white dwarf showing a continuous spectrum with no readily apparent lines. |
de Broglie equation hamugeš-e de Broglie Fr.: équation de de Broglie According to the → de Broglie hypothesis,
which has been verified by experiments, every → particle
of matter, whatever its nature, has a characteristic → wavelength
associated with its wavelike quantum aspect. The de Broglie equation gives the
equivalent wavelength of a moving particle: λ = h/mv, where h is
→ Planck's constant, m the mass of the particle,
and v its velocity. Named after Louis Victor de Broglie (1892-1987), French physicist, creator of a new field in physics, wave mechanics, who won the Nobel prize in physics in 1929. → equation |
de Broglie hypothesis engâre-ye de Broglie Fr.: hypothèse de de Broglie The suggestion by Louis de Broglie in 1924 whereby if → electromagnetic waves possess particle properties (→ particle nature), then it might be reasonable to suppose that material particles, such as → electrons, should possess wave properties (→ wave nature). The de Broglie hypothesis was based on the intuitive feeling that nature seems to have strong attachment to symmetry. In other words, if radiation has particle-like properties, then material particles should possess wave-like properties. At the time no direct experimental evidence was present for the validity of this suggestion. The first confirmation of de Broglie's hypothesis was provided by the → Davisson-Germer experiment. See also → wave-particle duality; |
de Broglie wavelength mowjtul-e de Broglie Fr.: longueur d'onde de Broglie The wavelength of the wave associated with a → particle as given by the → de Broglie equation. |
de Sitter Universe giti-ye de Sitter Fr.: Univers de de Sitter A solution to → Einstein's field equations of → general relativity which contains no ordinary matter (ΩM = 0) or radiation (ΩR = 0), is → Euclidean (k = 0), but has a → cosmological constant (ΩΛ > 0). The Universe expands exponentially forever. This solution was the first model expanding of → expanding Universe. See also → empty Universe, → Milne Universe. After the Dutch mathematician and physicist Willem de Sitter (1872-1934) who worked out the model in 1917; → universe. |
de Vaucouleurs law qânun-e de Vaucouleurs Fr.: loi de Vaucouleurs A mathematical expression describing the → surface brightness profile of a typical → elliptical galaxy, whereby the projected luminosity distribution varies as exp(-R)1/4. → de Vaucouleurs radius; → law. |
de Vaucouleurs radius šo'â'-e de Vaucouleurs Fr.: rayon de Vaucouleurs An → isophotal radius of a galaxy, where the → surface brightness in the B band falls to 25 mag arcsec-2. After the French-born American astronomer Gérard de Vaucouleurs (1918-1995); → radius. |
de Vaucouleurs system râžmân-e de Vaucouleurs Fr.: système de Vaucouleurs A widely used scheme for classifying galaxies which is an extension
to the → Hubble sequence
Hubble sequence. De Vaucouleurs introduced a more elaborate
classification system for spiral galaxies (→ spiral galaxy)
based on three morphological
characteristics: → de Vaucouleurs radius; → system. |
de- vâ- (#), foru- (#) Fr.: de- A prefix occurring in loanwords from L. to indicate: M.E., from O.Fr. de-, des-, partly from L. de- "from, down, away," and partly from L. → dis-. Prefix vâ- denoting "reversal, opposition; separation; repetition; open;
off; away,"
variant of bâz-, from Mid.Pers. abâz-, apâc-;
O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from,"
apaš [adv.] "toward the back;" cf. Skt. ápāñc
"situated behind." |
de-excitation foru-angizeš Fr.: désexcitation Transition from an excited energy state to a lower energy level, as in spectral line formation or particle emission from an atomic nucleus. From → de- + → excitation. |
de-orbit vâmadâridan Fr.: désorbiter To cause a spacecraft to leave its operational orbit to enter a descent phase or to change course. |
de-orbiting vâmadâreš Fr.: désorbitage Of a spacecraft, the act or process of departing from an operational orbit. → de-orbit. Noun form of → de-orbit. |
de-projection vâ-farâšâneš Fr.: déprojection A method for estimating the real orientation of a field and/or related velocities/separations from two-dimensional images. → de-; → projection. |
de-redden vâsorxidan Fr.: dérougir To correct the intensity or flux of a spectral line by eliminating the → reddening effect of → interstellar dust. De-redden, from → de- + redden verb of → red. Vâsorxidan, from vâ-, → de-, + sorxidan verb of sorx, → red. |
de-reddened magnitude borz-e vâsorxidé Fr.: magnitude dérougie A magnitude which has been corrected for the interstellar reddening. De-reddened, p.p. of → de-redden; → magnitude. Borz, → magnitude; vâsorxidé p.p. of vâsorxidan, → de-redden. |
de-reddening vâsorxeš Fr.: dérougissement The process that de-reddens. The state of being de-reddened. Verbal noun of → de-redden. |
deactivate foružirândan Fr.: désactiver To cause to be → inactive; remove the → effectiveness of (Dictionary.com). |
<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB 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 con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>
