Statistics: Any quantity calculated from the sample data which is used to give information about an unknown quantity in a population. For example, the sample mean is an estimator of the population mean.
Agent noun of → estimate.
1) That part of the mouth or lower course of a river in which the river's current
meets the sea's tide.
From L. aestuarium "a tidal marsh, mud-beds covered by water at high tides; channel inland from the sea," from aestus "boiling (of the sea), tide, heat," from PIE *aidh- "to burn;" cognates: Gk aithein "to burn," Skt. inddhe "burst into flames," O.Irish aed "fire," O.H.G. eit "funeral pile."
Kešandân, literally "site of tides," from kešand, → tide, + -ân a suffix of place and time.
Fr.: Eta de la Carène
The most luminous and the most extensively studied of → Luminous Blue Variables. Known also as HD 93308, it lies in the → Trumpler 16→ star cluster of the → Carina Nebula and is about 7,500 to 8,000 → light-years away. η Carina probably began its life as a → very massive star with an initial mass of about 150 → solar masses, and has a current estimated mass of about 90-100 solar masses. The difference has been lost in sudden giant eruptions in the past few thousand years. The so-called → Homunculus Nebula results from the mass ejection by η Carinae during its giant outburst around 1843 when it reached a magnitude of -1 and became the second brightest star in the southern sky. About 1880 it reached magnitude 7 and has remained at this level, although with fluctuations. The 1843 event ejected at least 12 solar masses of gas moving at speeds of up to 650 km s-1 with a kinetic energy of almost 1050 erg. The double-lobed remnant has a mass of about 2.5 solar masses. It is divided by a → torus of cold dust (110 K), about 5 → light-years in radius and 15 solar masses, which was ejected in an earlier event some 1000 years ago. There is strong evidence that η Carinae is a → binary system with a period of about 5.5 years and a projected separation less than 30 → astronomical units (about 0.013 arcsec). A colliding-wind binary is suggested by the → hard X-ray spectrum. The main component has an estimated → mass loss rate of 10-3 solar masses per year.
Eta (η), Gk. letter of alphabet; the → Carina constellation.
bâ tizâb kandan, ecidan
Fr.: graver à eau forte
1) To cut, bite, or corrode with an acid or the like; engrave with an
acid or the like, as to form a design in furrows that when charged
with ink will give an impression on paper.
From Du. etsen, from Ger. ätzen "to etch," from O.H.G. azzon "to cause to bite, feed," ultimately from PIE root *ed- "to eat;" cf. Av. ad- "to eat;" Mod.Pers. âš "thick brew, soup" (from O.Pers. *āšyā-, Proto-Ir. *HasH- "to eat"); Skt. ad- "to eat;" Gk. edo "I eat;" Lith. edu "I eat;" O.Irish ithim "I eat;" O.E. etan, O.H.G. essan, Ger. essen "to eat."
Bâ tizâb kandan, literally "to dig with acid," from bâ "with," tizâb "acid," kandan "to dig;" ecidan, from E. etch, cognate with Pers. âš, as above.
Fr.: gravure à eau forte
1) The act or process of making designs or pictures on a metal plate,
glass, etc., by the corrosive action of an acid instead of by a
Verbal noun of → etch.
From eth-, from → ethyl, + -ane a suffix used in names of hydrocarbons of the methane or paraffin series.
An → alcohol having molecular formula C2H5OH. It is a colorless inflammable liquid with a characteristic odor. Ethanol is produced by fermentation of sugar: C6H12O6 → 2 C2H5OH + 2 CO2. It is the active constituent of alcoholic beverages. It is used as a fuel and as a solvent in the extraction of specific substances. It is also known as → ethyl alcohol. Ethanol in the → interstellar medium was first detected toward the → Sagittarius B2 molecular cloud at 82.265, 90.118, and 104.809 GHz (B. Zuckerman et al. 1975, ApJ 196, L99).
Short for → ethyl alcohol.
1) Physics: A hypothetical medium filling all space formerly postulated to
account for the propagation of → electromagnetic radiation
through space. In order to facilitate description and to provide a physical explanation of
various phenomena involving action at a distance and electromagnetism, a medium
had been postulated with mechanical properties adjusted to provide a consistent theory.
In 1887 Michelson and Morley attempted to measure the motion of the Earth
through the ether. No such motion was detected. The
→ Michelson-Morley experiment has been repeated under
different conditions, but the hypothesis of a stationary ether through which the
Earth moves is not verified.
From L. æther "the upper air, pure air," from Gk. aither "upper air," from aithein "to burn, shine."
Fr.: entraînement de l'éther
A hypothesis put forward to explain the null measurement of the → ether drift. According to this hypothesis, the Earth somehow drags the ether with it as our planet rotates on its axis and revolves around the Sun. However, the ether drag hypothesis contradicts results from several experiments, including the → aberration of starlight.
Fr.: dérive de l'éther
1) The hypothetical motion of the supposed → ether relative to
the Earth. The → Michelson-Morley experiment found no
ether drift. An analogy is given by a boat drifting in a fast-flowing river due
to the river's current. With the same power, the speed would be slower
when sailing across the stream. Moreover, in order to reach
directly opposite the starting point, the boat would have to be headed
somewhat upstream. See also the → ether drag.
A combining form meaning "race, culture, people."
From Gk. ethnos "people, nation, class, tribe."
Qowm- loan from Ar. qaum "people, tribe, family."
The study of the beliefs, interpretations, and practices of specific cultures regarding celestial objects or phenomena. Ethnoastronomy uses the tools and methodologies of → ethnology in the study of astronomical conceptions.
The study of specific cultures (ethnic groups) in their different aspects (anthropological, social, cultural, etc.) to establish similarities and disparities between them.
A chemical group, C2H5, produced by removing a hydrogen atom from → ethane. For example, ethyl chloride is C2H5Cl
From Ger. Ethyl, from eth-, from → ether, + -yl a suffixed used in the names of radicals.
etil alkol (#)
Fr.: éthyl alcool
Same as → ethanol.
The study of the origins and history of the form and meaning of → words.
M.E., from L. etymologia, from Gk. etymologia, from etymon "true sense" (neuter of etymos) + logos, → -logy.
Riše-šenâsi, from rišé "root" (dialectal Tabari rexa; Kurd. regez, riše), from Mid.Pers. rêšak "root," maybe ultimately related to PIE *u(e)rad-, although the Skt. offshoot is absent (Gk. rhiza "root;" L. radix, radius "staff;" O.H.G. wurz "plant, herb;" Ger. Wurz; O.E. rot; E. root) + -šenâsi, → -logy.
A prefix meaning "good, well; true, genuine" (eupepsia; eukaryote); opposed to → dys-.
L. from Gk. eu "well," combining form of eus "good" (hu-gies "healthy"); cf. Mid.Pers. hu-; Av. hu- "good;" PIE base *su- "good," see below.
Mid.Pers. hu- "good, well" (hu-boy "sweet-smelling," hu-cihr "beautiful," hu-mânih "good-mindedness"); O.Pers. hu- "good, well" (ukāra- "having good people"); Av. hu-, hū- "well, good, beautiful" (hu-kərp- "well-shapen," hūxta- "well spoken," hu-manah- "good-minded"); Skt. su- "good" (svasti "well-being, good luck," sumánas- "good-minded," sūktá- "well spoken"); Gallic su-; O.S. su-; Welsh hy-; PIE base *su-, as above.
After the Gk. geometrician and educator at Alexandria, around 300 B.C., who applied the deductive principles of logic to geometry, thereby deriving statements from clearly defined axioms.
Fr.: division euclidienne
hendese-ye Oqlidosi (#)
Fr.: géométrie euclidienne
The geometry based on the postulates or descriptions of Euclid. One of the critical assumptions of the Euclidean geometry is given in his fifth postulate: through a point not on a line, one and only one line be drawn parallel to the given line. See also → non-Euclidean geometry.