<< < -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 Bok 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 MHD mic mid 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 > >>
Complete set of points in any given space group which are obtained by performing the symmetry operations of the space group on a single point (x, y, z).
Fr.: largeur équivalente
1) A measure of the → strength of a
→ spectral line. The equivalent width is the width of a
→ rectangle centered on a spectral line that, on a plot of
→ intensity against → wavelength,
has the same → area as the line.
Pâré asb (#), Korré Asb
Fr.: Petit Cheval
The Foal. A small, faint constellation in the northern hemisphere, lying between → Delphinus and → Pegasus, at 21h 10m right ascension, 5° north declination. Its brightest star, Kitalpha, has a visual magnitude of 3.9. Abbreviation: Equ; Genitive: Equulei.
L. Equuleus "little horse," diminutive of equus "horse," from PIE base *ekwos "horse" (cf. Pers. asb; Av. aspa- "horse;" Skt. áśva-; Gk. hippos; O.E. eoh; Arm. ēš). The origin of Equuleus is not clear. It is not mentioned in any classical Gk. or Roman myths. The first mention of the constellation was in Ptolemy's catalog, where it is referred to as Hippou Protome "the bust or upper part of an animal figure." Some mythologists have associated Equuleus with the foal Celeris, the brother of the winged horse Pegasus, given to Castor by Mercury.
Pâré asb "part of a horse," from
pâré "piece, part, portion, fragment" (Mid.Pers. pârag
"piece, part, portion; gift, offering, bribe;" Av. pāra- "debt," from
par- "to remunerate, equalize; to condemn;"
PIE *per- "to sell, hand over, distribute; to assign;" cf. L. pars
"part, piece, side, share," portio "share, portion;" Gk. peprotai
"it has been granted;" Skt. purti- "reward;" Hitt. pars-, parsiya-
"to break, crumble") + asb "horse," Mid.Pers. asb;
O.Pers. asa- "horse;" Av. aspa-
"horse," aspā- "mare," āsu.aspa- "unbound horse;"
Skt. áśvā- "mare;" cognate with L. equus, as above.
1) General: A period of time marked by a distinctive character,
From L.L. æra, era "fixed date, era, epoch from which time is reckoned," probably identical with L. æra "counters used for calculation," plural of aes "brass, money," from PIE *aus- "gold" (cf. Av. aiiah- "metal," aiianhaēna- "made of metal;" Skt. áyas- "metal;" O.H.G. ēr "ore;" O.E. ora "ore, unworked metal;" Ger. ehern "brazen").
Dowrân, from Ar. daur "age, time; revolution."
Fr.: méthode d'Eratosthène
A simple way of calculating the Earth's → circumference using two sticks and two theorems of the → Euclidean geometry. Eratosthenes calculated the length of a → meridian arc by measuring the shadow cast by a vertical → gnomon at noon on the → summer solstice. In Cyene (→ tropic of Cancer), no shadow is cast whereas in Alexandria, further north, the shadow is cast at an angle of 1/50 of 360° (measured using a → scaphe), or 7.2°, from the vertical. The circumference is therefore equal to 50 times the distance between the two cities. The distance from Syene to Alexandria was 5,000 stadia, which when multiplied by 50 gives the measure for the Earth's circumference, 250,000 stadia. Estimating the accuracy of this result is not easy because the unit of stadium is not uniquely defined in the ancient world. The most likely reconstruction puts Eratosthenes' stadium in the range 155-185m, implying an error of about 3% below or 15% above the true value. The modern value for the equatorial circumference of the Earth is 40,075 km. As scholars have pointed out, Eratosthenes' experiment was marred by several errors: Syene is not on the Tropic of cancer, it is not on the same meridian as Alexandria, and the distance between the two cities is less than he estimated. But the errors tended to cancel each other out, so his estimate was relatively accurate. See also: → Mamun's method, → Biruni's method.
Eratosthenes (c. 276-194 B.C.), Gk. mathematician, astronomer, and geographer. He studied in Athens and later became a librarian in Alexandria. His treatise On the Measuring of the Earth is lost. The account of his experiment has been preserved in Cleomedes (probably first century A.D.). See also → sieve of Eratosthenes; → experiment.
From Gk. ergon "work," from PIE base *werg- "to work" (cf. Av. varəz- "to work, do, perform, exercise;" Mod.Pers. varz-, varzidan "to labor, exercise, practise;" Arm. gorc "work;" Lith. verziu "tie, fasten, squeeze," vargas "need, distress;" Goth. waurkjan; O.E. wyrcan "work," wrecan "to drive, hunt, pursue").
The property of a dynamical system such that in an interval of sufficient duration, it will return to states that are closely similar to previous ones.
The study of the relationship between people and their working environment, in particular its effect on a person's efficiency. Ergonomics is applied in designing equipment and office systems to maximize productivity by reducing discomfort and fatigue of people in their workplace.
The region between the → event horizon and the → stationary limit of a rotating → Kerr black hole. It is possible for a particle falling inside the ergosphere to break into two parts, one of which will fall into the black hole and the other will come out.
The River. An extensive constellation in the southern hemisphere that takes windings between 1h20 and 5h 10m right ascension, 0° to 58° south declination. Despite its size, there are not many bright stars in this constellation. Notable are → Achernar and ε Eri, a dwarf star of magnitude 4.6 and type K2, which is just 10.7 light years away. Abbreviation: Eri; genitive: Eridani.
From Gk. Eridanos, a river god, a son of Oceanus and Tethys, and father of Zeuxippe. A purely mythical river which may have been named Eridanos ("Early Burnt") from the story of Phaethon, the boy who attempted to drive the chariot of the sun, and fell flaming into the waters of this mythical river.
Rud, → river.
A → dwarf planet which is a → trans-Neptunian object (TNO) with an orbital → eccentricity of 0.44, an → inclination of 44 degrees and a surface composition very similar to that of → Pluto. It orbits the Sun as far as twice Pluto's distance from the Sun. → Occultation observations carried out in 2010 were used to measure the size of Eris accurately. Eris's newly determined diameter is 2326±12 km. The observations show that Eris is an almost perfect twin of Pluto in size. They also reveal a very reflective surface, with an → albedo of 0.96, suggesting that it is uniformly covered in a thin layer of ice, probably a frozen atmosphere (Sicardy et al. 2011, Nature 478, 493). Like Pluto, Eris has a moon, which has been officially named by the → International Astronomical Union as (136199) Eris I (→ Dysnomia). The informal names of Eris were Xena and 2003 UB313.
Named after Eris the Gk. goddess of chaos and strife. She created a quarrel among goddesses that led to the Trojan War.
The act or state of eroding; state of being eroded.
From M.Fr. erosion, from L. erosionem (nom. erosio), from erodere "to gnaw away," from → ex- "away" + rodere "to gnaw, eat away" (cf. Fr. and E. animal rat).
Farsâyeš, from far- intensive prefix "much, abundant" (Mid.Pers. fra- "forward, before; much; around;" O.Pers. fra- "forward, forth;" Av. frā, fərā-, fra- "forward, forth; excessive;" cf. Skt. prá- "before; forward, in fron;" Gk. pro "before, in front of;" L. pro "on behalf of, in place of, before, for;" PIE *pro-) + verbal noun of sâyidan, variants sâbidan "to bruise, file," pasâvidan "to touch;" Khotanese sauy- "to rub;" Sogdian ps'w- "to touch;" Proto-Iranian *sau- "to rub."
Same as → Gamma Cephei.
From Ar. ar-râ'i (
irang (#), xatâ (#)
1) A deviation from accuracy or correctness; a mistake.
From O.Fr. erreur, from L. errorem (nom. error) "a wandering, straying, mistake," from errare "to wander."
Irang, from Mid.Pers. êrang "error, mistake;" xatâ, from Ar.
band-e irang, ~ xatâ
Fr.: barre d'erreur
On a graph displaying the results of a measurement, the dash used to indicate the confidence range of the value attributed to a quantity.
→ error; bar, from O.Fr. barre, from V.L. *barra "bar, barrier," or perhaps from Gaulish *barro "summit."
Band "that which closes, shuts, blocks," from bastan, band- "to shut, bind," from Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie" (cf. Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind;" Ger. binden; E. bind); → error.
Fr.: entrer en éruption
To burst forth; to eject matter (of a star, volcano, geyser, etc.). → eruptive variable.
From L eruptus "burst forth, broken out," p.p. of erumpere "to break out, burst forth," from → ex- "out" + rumpere "to break, rupture."
Osdaridan, from os-, → ex- + daridan "to tear, rend, lacerate;" Mid.Pers. darridan "to tear, split;" Av. dar- "to tear," dərəta- "cut," auua.dərənant- "shattering;" cf. Skt. dar- "to crack, split, break, burst," darati "he splits;" Gk. derein "to flay," derma "skin;" P.Gmc. *teran; O.E. teran; E. tear; Ger. zerren "to pull, to tear," zehren "to undermine, to wear out;" PIE base *der- " to split, peel, flay."
1) An act, process, or instance of erupting; something that is erupted or ejected.
Verbal noun of → erupt.
Relating to, formed by, characterized by, or producing → eruption.
Fr.: objet éruptif
Fr.: protubérance éruptive
A huge solar prominence which has previously been quiescent but suddenly starts to lift up from the → photosphere with velocities of several hundred km/s and escapes into the → interplanetary space. Eruptive prominences with the highest velocities have been observed at 1300 km/s, reaching heights of 1 million km above the photosphere. Such prominences are often observed at the solar limb, in association with → coronal mass ejections. On the Sun's disk, the equivalent phenomenon is an eruptive filament.