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non-Euclidean geometry

(Encyclopedia)non-Euclidean geometry, branch of geometry in which the fifth postulate of Euclidean geometry, which allows one and only one line parallel to a given line through a given external point, is replaced b...

Cleveland, cities, United States

(Encyclopedia)Cleveland. 1 City (2020 pop. 372,674), seat of Cuyahoga co., NE Ohio, on Lake Erie at the mouth of the Cuyahoga River; laid out (1796) by Moses ...

progressive education

(Encyclopedia)progressive education, movement in American education. Confined to a period between the late 19th and mid-20th cent., the term “progressive education” is generally used to refer only to those educ...

reflection

(Encyclopedia)CE5 Image formation by curved mirrors and lenses reflection, return of a wave from a surface that it strikes into the medium through which it has traveled. The general principles governing the ref...

Ruscha, Ed

(Encyclopedia)Ruscha, Ed (Edward Joseph Ruscha 4th) ro͞oshāˈ [key], 1937–, American artist, b. Omaha, Neb. He is closely associated with Los Angeles, where he moved to attend (1956–60) the Chouinard Art Inst...

Saint Paul's Cathedral

(Encyclopedia)Saint Paul's Cathedral, London, masterpiece of Sir Christopher Wren and one of the finest church designs of the English baroque. It stands at the head of Ludgate Hill, where, according to tradition, a...

3D printer

(Encyclopedia)3D printer, computerized device that produces a three-dimensional object by creating it as a series of thin layers. The object is created from a model stored in computer-aided design file; the model i...

Rijksmuseum

(Encyclopedia)Rijksmuseum rīksˈmyo͞ozēˌəm [key], Dutch national museum in Amsterdam, founded in 1808 by Louis Bonaparte, king of Holland (see under Bonaparte), as the Great Royal Museum in the Royal Palace. I...

shaft sinking

(Encyclopedia)shaft sinking, excavation from the surface of an opening in the earth. Shafts, which are generally vertical, are usually distinguished from tunnels, which are horizontal. Little difficulty is experien...

typewriter

(Encyclopedia)typewriter, instrument for producing by manual operation characters similar to those of printing. Corresponding to each key on the instrument's keyboard is a steel type. Activated through a series of ...