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thunder
(Encyclopedia)thunder, sound produced along a path of a lightning flash, caused by the rapid heating and expansion of the adjacent air; lightning can heat air to temperatures as much as five times hotter than those...Adhara
(Encyclopedia)Adhara ădhârˈə [key], bright star in the constellation Canis Major; Bayer designation ε Canis Majoris; 1992 position R.A. 6h58.3m, Dec. −31°54′. A bluish-white giant (spectral class B2 II) w...navigation
(Encyclopedia)navigation, science and technology of finding the position and directing the course of vessels and aircraft. The next great revolution in navigation occurred in the 20th cent., when radio signals ...spectral class
(Encyclopedia) CE5 spectral class, in astronomy, a classification of the stars by their spectrum and luminosity. In 1885, E. C. Pickering began the first extensive attempt to classify the stars spectroscopically....week
(Encyclopedia)week, period of time shorter than the month, commonly seven days. The ancient Egyptians used a 10-day period, as did the French under the short-lived French Revolutionary calendar. In many regions a f...supernova
(Encyclopedia)supernova, a massive star in the latter stages of stellar evolution that suddenly contracts and then explodes, increasing its energy output as much as a billionfold. Supernovas are the principal distr...time , sequential arrangement of all events
(Encyclopedia)time, sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophi...raffia
(Encyclopedia)raffia rāˈfēə [key], fiber obtained from the raffia palm of Madagascar, exported for various uses, such as tying up plants that require support, binding together vegetables to be marketed, and wea...Sorabji, Cornelia
(Encyclopedia)Sorabji, Cornelia sōräbˈjē [key], c.1870–1954, Indian lawyer and author. She took a law degree at Oxford in 1893. She served (1904–23) as a special legal adviser to the Court of Wards of Benga...sky
(Encyclopedia)sky, apparent dome over the earth, background of the clouds, sun, moon, and stars. The blue color of the clear daytime sky results from the selective scattering of light rays by the minute particles o...Browse by Subject
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