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Nevada

(Encyclopedia)CE5 Nevada nəvădˈə, –vä– [key], far western state of the United States. It is bordered by Utah (E), Arizona (SE), California (SW, W), and Oregon and Idaho (N). In the 20th cent. the ...

stellar evolution

(Encyclopedia)CE5 The above Hertzsprung-Russell (H-R) diagram shows the track of stellar evolution for a typical star. After spending much of its life evolving toward or along the main sequence, the star becomes...

atom

(Encyclopedia)CE5 Bohr-Rutherford atom CE5 Probability distribution of the electron in the hydrogen atom: A. Ground state B. Highly excited state atom [Gr.,=uncuttable (indivisible)], basic unit of matte...

air pollution

(Encyclopedia)air pollution, contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health. The major sources of air pollution are t...

chemistry

(Encyclopedia)chemistry, branch of science concerned with the properties, composition, and structure of substances and the changes they undergo when they combine or react under specified conditions. Organic chemi...

space exploration

(Encyclopedia)CE5 Moon mission assembly CE5 Stages in a moon mission shown counterclockwise from launching on the first day to splashdown on the ninth day. space exploration, the investigation of physical co...

dog

(Encyclopedia)CE5 General anatomy of a dog dog, carnivorous, domesticated wolf (Canis lupus familiaris) of the family Canidae, to which the jackal, fox, and tanuki also belong. The family Canidae is sometimes r...

dating

(Encyclopedia)dating, the determination of the age of an object, of a natural phenomenon, or of a series of events. There are two basic types of dating methods, relative and absolute. In relative dating, the tempor...

Oklahoma

(Encyclopedia)CE5 Oklahoma ōkləhōˈmə [key], state in SW United States. It is bordered by Missouri and Arkansas (E); Texas, partially across the Red River (S, W); New Mexico, across the narrow edge of the Ok...

Iowa, state, United States

(Encyclopedia)CE5 Iowa īˈəwə [key], midwestern state in the N central United States. It is bounded by the Mississippi River, across which lie Wisconsin and Illinois (E); Missouri (S); Nebraska and South Dako...