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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; ...

gas laws

(Encyclopedia)gas laws, physical laws describing the behavior of a gas under various conditions of pressure, volume, and temperature. Experimental results indicate that all real gases behave in approximately the sa...

Hubble's law

(Encyclopedia)Hubble's law, in astronomy, statement that the distances between galaxies (see galaxy) or clusters of galaxies are continuously increasing and that therefore the universe is expanding. Hubble's law ...

Rydberg, Johannes Robert

(Encyclopedia)Rydberg, Johannes Robert yo͞oˈhänəs rôˈbərt rüdˈbĕryə [key], 1854–1919, Swedish physicist. Rydberg was a professor at Lund from 1901 to 1919. He is best known for his grouping of the freq...

constipation

(Encyclopedia)constipation, infrequent or difficult passage of feces. Constipation may be caused by the lack of adequate roughage or fluid in the diet, prolonged physical inactivity, certain drugs, or emotional dis...

Parkes, Sir Henry

(Encyclopedia)Parkes, Sir Henry, 1815–96, Australian political leader, b. England. He emigrated to Australia in 1839 and later founded a newspaper, the Empire, to advocate responsible government and an end to the...

celestial sphere

(Encyclopedia)celestial sphere, imaginary sphere of infinite radius with the earth at its center. It is used for describing the positions and motions of stars and other objects. For these purposes, any astronomical...

Vladimir II

(Encyclopedia)Vladimir II (Vladimir Monomakh) or Volodymyr II, 1053–1125, grand duke of Kiev (1113–25); son of Vsevolod I, prince of Pereyaslavl and grand duke of Kiev (ruled 1078–93). On his father's death h...

Boleslav I

(Encyclopedia)Boleslav I bōˈləsläfˌ [key], d. 967, duke of Bohemia (929–67). He became duke by assassinating his elder brother, Duke Wenceslaus (see Wenceslaus, Saint). Although Boleslav was involved in cons...

activation energy

(Encyclopedia)CE5 Energy profile of an exothermic reaction: Although the total energy of the products is less than that of the reactants, the activation energy must be added to weaken or break existing bonds bef...