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mining

(Encyclopedia)mining, extraction of solid mineral resources from the earth. These resources include ores, which contain commercially valuable amounts of metals, such as iron and aluminum; precious stones, such as d...

metallurgy

(Encyclopedia)metallurgy mĕtˈəlûrˌjē [key], science and technology of metals and their alloys. Modern metallurgical research is concerned with the preparation of radioactive metals, with obtaining metals econ...

relativity

(Encyclopedia)relativity, physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference. One consequ...

small arms

(Encyclopedia)small arms, firearms designed primarily to be carried and fired by one person and, generally, held in the hands, as distinguished from heavy arms, or artillery. Automatic small arms were develope...

battery, electric

(Encyclopedia)CE5 Lead storage cell: At the lead-dioxide electrode, electrons from the circuit combine with lead dioxide and sulfuric acid to form lead sulfate and water. At the spongy-lead electrode, lead react...

element

(Encyclopedia)CE5 element, in chemistry, a substance that cannot be decomposed into simpler substances by chemical means. A substance such as a compound can be decomposed into its constituent elements by means o...

earth, in geology and astronomy

(Encyclopedia)CE5 A. Cross section of the earth, showing its shells B. Detailed cross section of the crust and upper mantle: The lithosphere consists of the hard rock in the crust and upper mantle, lying above t...

North America

(Encyclopedia)CE5 North America, third largest continent (2015 est. pop. 571,949,000), c.9,400,000 sq mi (24,346,000 sq km), the northern of the two continents of the Western Hemisphere. North America includes a...

Slovenia

(Encyclopedia)CE5 Slovenia slōvēˈnēə [key], Slovene Slovenija, officially Republic of Slovenia, republic (2015 est. pop. 2,075,000), 7,817 sq mi (20,246 sq km). It is bounded in the north by Austria, in the...

Kyrgyzstan

(Encyclopedia)CE5 Kyrgyzstan kērgĭstänˈ [key], officially Kyrgyz Republic, republic (2015 est. pop. 5,865,000), c.76,600 sq mi (198,400 sq km), central Asia. It borders on China in the southeast, on Kazakhst...