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black hole

(Encyclopedia)black hole, in astronomy, celestial object of such extremely intense gravity that it attracts everything near it and in some instances prevents everything, including light, from escaping. The term was...

Southeast Asian languages

(Encyclopedia)Southeast Asian languages, family of languages, sometimes also called Austroasiatic, spoken in SE Asia by about 80 million people. According to one school of thought, it has three subfamilies: the Mon...

Brachiopoda

(Encyclopedia)CE5 Internal anatomy of a lamp shell, Magellania, representative of the phylum Brachiopoda Brachiopoda brākēŏpˈədə [key], phylum of shelled sessile or sedentary marine animals, commonly know...

atmosphere

(Encyclopedia)CE5 Atmosphere atmosphere [Gr.,=sphere of air], the mixture of gases surrounding a celestial body with sufficient gravity to maintain it. Although some details about the atmospheres of other plane...

Mastigophora

(Encyclopedia)Mastigophora măsˌtĭgŏfˈərə [key], phylum of unicellular heterotrophic protozoans of the kingdom Protista. Most of the approximately 1,500 species of Mastigophora are propelled by one or more fl...

sand dollar

(Encyclopedia)sand dollar, common name for a marine animal in the same phylum as the starfish (see sea star). The sand dollar has a rigid, flattened, disk-shaped test, or shell, made of firmly united plates lying j...

thermionic emission

(Encyclopedia)thermionic emission thûrmˌīŏnˈĭk [key], emission of electrons or ions by substances that are highly heated, the charged particles being called thermions. The number of thermions emitted increase...

shipworm

(Encyclopedia)shipworm or teredo tĕrēˈdō [key], marine bivalve mollusk of the family Teredinidae, specialized for boring in wood. A shipworm is not a worm, but a greatly elongated clam. Its two shells, enclosin...

corona, in astronomy

(Encyclopedia)corona, luminous envelope surrounding the sun, outside the chromosphere. Its density is less than one billionth that of the earth's atmosphere. The corona is visible only at the time of totality durin...

Democritus

(Encyclopedia)Democritus dĭmŏkˈrĭtəs [key], c.460–c.370 b.c., Greek philosopher of Abdera; pupil of Leucippus. His theory of the nature of the physical world was the most radical and scientific attempted up ...