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navigation

(Encyclopedia)navigation, science and technology of finding the position and directing the course of vessels and aircraft. The next great revolution in navigation occurred in the 20th cent., when radio signals ...

telephone

(Encyclopedia)CE5 Hand telephone telephone, device for communicating sound, especially speech, usually by means of wires in an electric circuit. The telephones now in general use evolved from the device invente...

Beethoven, Ludwig van

(Encyclopedia)Beethoven, Ludwig van lŭdˈwĭg văn bāˈtōvən, Ger. lo͝otˈvĭkh fän bātˈhōfən [key], 1770–1827, German composer. He is universally recognized as one of the greatest composers of the West...

infrared astronomy

(Encyclopedia)infrared astronomy, study of celestial objects by means of the infrared radiation they emit, in the wavelength range from about 1 micrometer to about 1 millimeter. All objects, from trees and building...

petroleum

(Encyclopedia)petroleum, oily, flammable liquid that occurs naturally in deposits, usually beneath the surface of the earth; it is also called crude oil. It consists principally of a mixture of hydrocarbons, with t...

Philadelphia, city, United States

(Encyclopedia)Philadelphia, city (2020 pop. 1,603,797), coextensive with Philadelphia co., SE Pa., on the Delaware River c.100 mi (160 km) upstream at the influx of t...

cell, in biology

(Encyclopedia)CE5 Animal cell cell, in biology, the unit of structure and function of which all plants and animals are composed. The cell is the smallest unit in the living organism that is capable of integrati...

colloid

(Encyclopedia)colloid kŏlˈoid [key] [Gr.,=gluelike], a mixture in which one substance is divided into minute particles (called colloidal particles) and dispersed throughout a second substance. The mixture is also...

deafness

(Encyclopedia)deafness, partial or total lack of hearing. It may be present at birth (congenital) or may be acquired at any age thereafter. A person who cannot detect sound at an amplitude of 20 decibels in a frequ...

pressure

(Encyclopedia)pressure, in mechanics, ratio of the force acting on a surface to the area of the surface; it is thus distinct from the total force acting on a surface. A force can be applied to and sustained by a si...