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Catskill Mountains

(Encyclopedia)Catskill Mountains, dissected plateau of the Appalachian Mt. system, SE N.Y., W of the Hudson River. This glaciated region, wooded and rolling, with deep gorges and many waterfalls, is drained by the ...

Sommerfeld, Arnold Johannes Wilhelm

(Encyclopedia)Sommerfeld, Arnold Johannes Wilhelm ärˈnōlt yōhänˈəs vĭlˈhĕlm zômˈərfĕlt [key], 1868–1951, German physicist and teacher. He received a Ph.D. at Königsburg Univ. in 1891 and was a prof...

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...

Laurent, Auguste

(Encyclopedia)Laurent, Auguste ōgüstˈ lōräNˈ [key], 1808–53, French organic chemist. He devised a systematic nomenclature for organic chemistry. His studies on naphthalene and its chlorination products led ...

ether, in physics and astronomy

(Encyclopedia)ether or aether, in physics and astronomy, a hypothetical medium for transmitting light and heat (radiation), filling all unoccupied space; it is also called luminiferous ether. In Newtonian physics a...

Gerhardt, Charles Frédéric

(Encyclopedia)Gerhardt, Charles Frédéric shärl frādārēkˈ zhārärˈ [key], 1816–56, French chemist, b. Strasbourg. He revived the theory of acid radicals, which he called the theory of residues, and did va...

Seeger, Pete

(Encyclopedia)Seeger, Pete (Peter Seeger), 1919–2014, American folksinger, composer, and environmentalist, b. New York City. Seeger, a son of musicologist Charles Seeger and violinist Constance Edson Seeger, step...

Lucas, Robert Emerson, Jr.

(Encyclopedia)Lucas, Robert Emerson, Jr., 1937–2023, American economist, b. Yakima, Wash., Ph.D. Univ. of Chicago, 1964. Lucas taught at Carnegie Mellon Univ. (1963...

Young, Thomas

(Encyclopedia)Young, Thomas, 1773–1829, English physicist, physician, and Egyptologist. He established (1799) a medical practice in London and was elected (1811) to the staff of St. George's Hospital there. His l...

hurdy-gurdy

(Encyclopedia)CE5 Hurdy-gurdy hurdy-gurdy, musical instrument with three strings that are caused to vibrate by a wooden wheel turned by a crank. Stopping is accomplished by keys that usually affect only the str...