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conservation laws

(Encyclopedia)conservation laws, in physics, basic laws that together determine which processes can or cannot occur in nature; each law maintains that the total value of the quantity governed by that law, e.g., mas...

nucleus, in physics

(Encyclopedia)nucleus, in physics, the extremely dense central core of an atom. Following the discovery of radioactivity by A. H. Becquerel in 1896, Ernest Rutherford identified two types of radiation given off b...

lepton

(Encyclopedia)lepton lĕpˈtŏnˌ [key] [Gr.,=light (i.e., lightweight)], class of elementary particles that includes the electron and its antiparticle, the muon and its antiparticle, the tau and its antiparticle, ...

momentum

(Encyclopedia)momentum mōmĕnˈtəm [key], in mechanics, the quantity of motion of a body, specifically the product of the mass of the body and its velocity. Momentum is a vector quantity; i.e., it has both a magn...

Tecumseh

(Encyclopedia)Tecumseh tĭkŭmˈsē [key], 1768?–1813, chief of the Shawnee, b. probably in Clark co., Ohio. Among his people he became distinguished for his prowess in battle, but he opposed the practice of tort...

Root, Elihu

(Encyclopedia)Root, Elihu, 1845–1937, American cabinet member and diplomat, b. Clinton, N.Y. Admitted to the bar in 1867, he practiced law in New York City, became prominent in Republican politics, and was appoin...

Conrad II, ruler of the Holy Roman Empire

(Encyclopedia)Conrad II, c.990–1039, Holy Roman emperor (1027–39) and German king (1024–39), first of the Salian dynasty of the Holy Roman Empire. With the end of the Saxon line on the death of Henry II, the ...

Granger movement

(Encyclopedia)Granger movement, American agrarian movement taking its name from the National Grange of the Patrons of Husbandry, an organization founded in 1867 by Oliver H. Kelley and six associates. Its local uni...

fugue

(Encyclopedia)fugue fyo͞og [key] [Ital.,=flight], in music, a form of composition in which the basic principle is imitative counterpoint of several voices. Its main elements are: (1) a theme, or subject, stated fi...

Herriot, Édouard

(Encyclopedia)Herriot, Édouard ādwärˈ ĕryōˈ [key], 1872–1957, French statesman and man of letters. After beginning an academic career he turned to politics. A moderate leftist, anticlerical, and antimilita...