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quantum electrodynamics
(Encyclopedia)quantum electrodynamics (QED), quantum field theory that describes the properties of electromagnetic radiation and its interaction with electrically charged matter in the framework of quantum theory. ...vector
(Encyclopedia)vector, quantity having both magnitude and direction; it may be represented by a directed line segment. Many physical quantities are vectors, e.g., force, velocity, and momentum. Thus, in specifying a...probability
(Encyclopedia)probability, in mathematics, assignment of a number as a measure of the “chance” that a given event will occur. There are certain important restrictions on such a probability measure. In any exper...algebra
(Encyclopedia)algebra, branch of mathematics concerned with operations on sets of numbers or other elements that are often represented by symbols. Algebra is a generalization of arithmetic and gains much of its pow...ecology
(Encyclopedia)ecology, study of the relationships of organisms to their physical environment and to one another. The study of an individual organism or a single species is termed autecology; the study of groups of ...logic
(Encyclopedia)logic, the systematic study of valid inference. A distinction is drawn between logical validity and truth. Validity merely refers to formal properties of the process of inference. Thus, a conclusion w...atmosphere
(Encyclopedia)CE5 Atmosphere atmosphere [Gr.,=sphere of air], the mixture of gases surrounding a celestial body with sufficient gravity to maintain it. Although some details about the atmospheres of other plane...astronomy
(Encyclopedia)astronomy, branch of science that studies the motions and natures of celestial bodies, such as planets, stars, and galaxies; more generally, the study of matter and energy in the universe at large. ...mathematics
(Encyclopedia)mathematics, deductive study of numbers, geometry, and various abstract constructs, or structures; the latter often “abstract” the features common to several models derived from the empirical, or ...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...Browse by Subject
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