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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...

Lorentz, Hendrik Antoon

(Encyclopedia)Lorentz, Hendrik Antoon hĕnˈdrək änˈtōn lōˈrĕnts [key], 1853–1928, Dutch physicist, a pioneer in formulating the relations between electricity, magnetism, and light. He was one of the first...

Appaloosa horse

(Encyclopedia)Appaloosa horse ăpˌəlo͞oˈsə [key], breed of light horse developed in the United States by the Nez Percé of Idaho from a horse that originated in Asia and was popular in Europe during the Middle...

electromagnetic radiation

(Encyclopedia)CE5 Electromagnetic spectrum electromagnetic radiation, energy radiated in the form of a wave as a result of the motion of electric charges. A moving charge gives rise to a magnetic field, and if ...

radar astronomy

(Encyclopedia)radar astronomy, application of radar to the determination of distances and planetary features within the solar system, such as rotation rates. A short burst of radio waves is transmitted in the direc...

Beaufort scale

(Encyclopedia)Beaufort scale, a scale of wind velocity devised (c.1805) by Admiral Sir Francis Beaufort of the British navy. An adaptation of Beaufort's scale is used by the U.S. National Weather Service; it employ...

spectrum

(Encyclopedia)CE5 Dispersion of white light by a triangular prism spectrum, arrangement or display of light or other form of radiation separated according to wavelength, frequency, energy, or some other propert...

ceilometer

(Encyclopedia)ceilometer sēlŏmˈĭtər [key], in aviation and meteorology, automatic instrument used to record ceiling, i.e., the altitude of the lowest cloud layer covering more than half of the sky. The ceilome...

Maxwell, James Clerk

(Encyclopedia)Maxwell, James Clerk klärk [key], 1831–79, great Scottish physicist. After a brilliant career at Edinburgh and Cambridge, where he won early recognition with mathematical papers, he was a professor...

Thoroughbred horse

(Encyclopedia)Thoroughbred horse, breed of light horse more properly known as the English running horse. As its name implies, it was the first pedigreed, or “thoroughbred” horse. It originated in England from c...