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hertz

(Encyclopedia)hertz hûrts [key] [for Heinrich R. Hertz], abbr. Hz, unit of frequency, equal to 1 cycle per second. The term is combined with metric prefixes to denote multiple units such as the kilohertz (1,000 Hz...

Holston

(Encyclopedia)Holston, river, c.120 mi (190 km) long, formed by the uniting of its northern and southern forks, NE Tenn., and flowing SW through the Great Appalachian Valley, joining the French Broad River at Knoxv...

power, in physics

(Encyclopedia)power, in physics, time rate of doing work or of producing or expending energy. The unit of power based on the English units of measurement is the horsepower, devised for describing mechanical power b...

Lacaille, Nicolas Louis de

(Encyclopedia)Lacaille, Nicolas Louis de nēkôläˈ lwē də läkäˈyə [key], 1713–62, French astronomer. As a result of his success in making meridional measurements in France under the patronage of the duke ...

Ghez, Andrea Mia

(Encyclopedia)Ghez, Andrea Mia, 1965–, American astrophysicist, b. New York City, Ph.D. California Institute of Technology, 1992. She has been on the faculty at the Univ. of California, Los Angeles, since 1994. G...

Huggins, Sir William

(Encyclopedia)Huggins, Sir William, 1824–1910, English astronomer. Using a spectroscope, he began to study the chemical constitution of stars from the observatory attached to his home in Tulse Hill, London. He pr...

Wood, Robert Williams

(Encyclopedia)Wood, Robert Williams, 1868–1955, American physicist, b. Concord, Mass., grad. Harvard (B.A., 1891). After studying abroad he became associated with Johns Hopkins as professor of experimental physic...

Cannon, Annie Jump

(Encyclopedia)Cannon, Annie Jump, 1863–1941, American astronomer, b. Dover, Del. In 1897 she became an assistant in the Harvard College Observatory, where (1911–38) she was astronomer and curator of astronomica...

Ptolemy

(Encyclopedia)Ptolemy (Claudius Ptolemaeus), fl. 2d cent. a.d., celebrated Greco-Egyptian mathematician, astronomer, and geographer. He made his observations in Alexandria and was the last great astronomer of ancie...

Cockrell, Francis Marion

(Encyclopedia)Cockrell, Francis Marion kŏkˈrəl [key], 1834–1915, Confederate general and U.S. senator, b. Johnson co., Mo. Enlisting as a private with Confederate forces in the Civil War, he became a brigadier...