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Philomena of Dacia, Peter

(Encyclopedia)Philomena of Dacia, Peter, or Peter Nightingale, fl. 1291–1303, Danish astronomer and mathematician. He taught at the Univ. of Bologna (1291–92) and in Paris, and was a canon of Roskilde Cathedral...

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...

short waves

(Encyclopedia)short waves, radio waves whose frequencies range from about 3 to 25 megahertz (Mhz), corresponding roughly to the high-frequency band (see radio frequency). When they impinge on certain layers of the ...

distortion

(Encyclopedia)distortion, in electronics, undesired change in an electric signal waveform as it passes from the input to the output of some system or device. In an audio system, distortion results in poor reproduct...

vibration

(Encyclopedia)vibration, in physics, commonly an oscillatory motion—a movement first in one direction and then back again in the opposite direction. It is exhibited, for example, by a swinging pendulum, by the pr...

Banneker, Benjamin

(Encyclopedia)Banneker, Benjamin, 1731–1806, African-American inventor, astronomer, and mathematician, b. Baltimore co., Md., at what is now Ellicott's Mills. A free black, Banneker was essentially self-taught. H...

moon

(Encyclopedia)CE5 The moon: Near side CE5 The moon: Far side moon, natural satellite of a planet (see satellite, natural) or dwarf planet, in particular, the single natural satellite of the earth. It is no...

New Albany

(Encyclopedia)New Albany, city (1990 pop. 36,322), seat of Floyd co., S Ind., near the falls of the Ohio River opposite Louisville, Ky.; inc. 1819. The city was a shipbuilding center in the 19th cent., and the rive...

multiplexing

(Encyclopedia)multiplexing, in communication, technique whereby two or more independent messages, or information-bearing signals, are carried by a single common medium, or channel. When multiplexing is performed, t...

magnetic resonance

(Encyclopedia)magnetic resonance, in physics and chemistry, phenomenon produced by simultaneously applying a steady magnetic field and electromagnetic radiation (usually radio waves) to a sample of atoms and then a...