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Fizeau, Armand Hippolyte Louis

(Encyclopedia)Fizeau, Armand Hippolyte Louis ärmäNˈ ēpôlētˈ lwē fēzōˈ [key], 1819–96, French physicist. The first to measure (1849) the velocity of light in air, he also determined its speed in water. ...

Rømer, Olaus

(Encyclopedia)Rømer, Olaus or Ole ōläˈo͝os, ōˈlə römˈər [key], 1644–1710, Danish astronomer. He is noted for his discovery that light travels at a definite speed and does not move through space instant...

stroboscope

(Encyclopedia)stroboscope strŏbˈəskōp [key], optical instrument for making a moving object appear to be slowed down or stationary. This effect is created by interrupting the observer's view so that the object i...

Tamm, Igor Yevgenyevich

(Encyclopedia)Tamm, Igor Yevgenyevich, 1895–1971, Soviet physicist, Ph.D. Moscow State Univ., 1933. He was a researcher at the P. N. Lebedev Physical Institute in Moscow from 1934 until his death in 1971. Tamm an...

Frank, Ilya Mikhailovich

(Encyclopedia)Frank, Ilya Mikhailovich, 1908–90, Soviet physicist, Ph.D. Moscow State Univ., 1935. He was a professor at Moscow State Univ. from 1944 until his death in 1990. Mikhailovich and Igor Y. Tamm won the...

ground speed indicator

(Encyclopedia)ground speed indicator: see air navigation. ...

Arabian horse

(Encyclopedia)Arabian horse, breed of light horse developed in Mesopotamia and N Africa, and probably the first true domesticated breed. Prized since earliest times for its superior beauty, spirit, speed, grace of ...

motion

(Encyclopedia)motion, the change of position of one body with respect to another. The rate of change is the speed of the body. If the direction of motion is also given, then the velocity of the body is determined; ...

Foucault, Jean Bernard Léon

(Encyclopedia)Foucault, Jean Bernard Léon zhäN bĕrnärˈ lāôNˈ fo͞okōˈ [key], 1819–68, French physicist. Known especially for his research on the speed of light, he determined its velocity in air and fou...

Archimedes' screw

(Encyclopedia)Archimedes' screw, a simple mechanical device believed to have been invented by Archimedes in the 3d cent. b.c. It consists of a cylinder inside of which a continuous screw, extending the length of th...