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photoelectric effect

(Encyclopedia)photoelectric effect, emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory ...

Sacks, Oliver Wolf

(Encyclopedia)Sacks, Oliver Wolf, 1933–2015, British neurologist and author, b. London, educated at Queen's College, Oxford. In 1960 he moved to the United States, where he continued his medical training. He bega...

Trent Affair

(Encyclopedia)Trent Affair, incident in the diplomatic relations between the United States and Great Britain, which occurred during the American Civil War. On Nov. 8, 1861, the British mail packet Trent, carrying J...

Oran

(Encyclopedia)Oran ôräNˈ [key], city (1998 pop. 692,516), capital of Oran prov., NW Algeria, a port on the Gulf of Oran of the Mediterranean Sea. One of the country's leading ports, it ships wheat, wine, alcohol...

californium

(Encyclopedia)californium kălˈĭfôrˌnēəm [key] [from California], artificially produced, radioactive metallic chemical element; symbol Cf; at. no. 98; mass no. of most stable isotope 251; m.p. about 900℃; b...

Hohenzollern, German princely family

(Encyclopedia)Hohenzollern hōˌən-tsôlˈərn [key], German princely family that ruled Brandenburg (1415–1918), Prussia (1525–1918), and Germany (1871–1918). Originating in S Germany and traceable to the 11...

Lewis and Clark expedition

(Encyclopedia)Lewis and Clark expedition, 1803–6, U.S. expedition that explored the territory of the Louisiana Purchase and the country beyond as far as the Pacific Ocean. The men were gathered and in the winte...

Maastricht

(Encyclopedia)Maastricht mäsˈtrĭkhtˌ [key], city (1994 pop. 118,102), capital of Limburg prov., SE Netherlands, on the Maas (Meuse) River and on the Albert Canal system. It is an important rail and river transp...

Dampier, William

(Encyclopedia)Dampier, William dămˈpēr [key], 1651–1715, English explorer, buccaneer, hydrographer, and naturalist. He fought (1673) in the Dutch War, managed a plantation in Jamaica (1674), and then worked wi...

dark energy

(Encyclopedia)dark energy, repulsive force that opposes the self-attraction of matter (see gravitation) and causes the expansion of the universe to accelerate. The search for dark energy was triggered by the discov...