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Brooklyn Academy of Music

(Encyclopedia)Brooklyn Academy of Music, performing arts center located in the borough of Brooklyn, N.Y. and popularly known as BAM. Founded in 1859 and opened in 1861, it is the oldest such institution still in op...

proper motion

(Encyclopedia)proper motion, in astronomy, apparent movement of a star on the celestial sphere, usually measured as seconds of arc per year; it is due both to the actual relative motions of the sun and the star thr...

field, in physics

(Encyclopedia)field, in physics, region throughout which a force may be exerted; examples are the gravitational, electric, and magnetic fields that surround, respectively, masses, electric charges, and magnets. The...

antenna

(Encyclopedia)antenna ăntĕnˈə [key], in electronics, system of wires or other conductors used to transmit or receive radio or other electromagnetic waves (see radio); sometimes called an aerial. The idea of usi...

Lorentz contraction

(Encyclopedia)Lorentz contraction lôrˈĕnts [key], in physics, contraction or foreshortening of a moving body in the direction of its motion, proposed by H. A. Lorentz on theoretical grounds and based on an earli...

acoustics

(Encyclopedia)acoustics əko͞oˈstĭks [key] [Gr.,=the facts about hearing], the science of sound, including its production, propagation, and effects. Various branches of acoustics that deal with different aspects...

mirror

(Encyclopedia)mirror, in optics, a reflecting surface that forms an image of an object when light rays coming from that object fall upon it (see reflection). Usually mirrors are made of plate glass, one side of whi...

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...

color index

(Encyclopedia)color index, in astronomy, difference in an object's brightness as recorded between any two well-defined bands of the electromagnetic spectrum by using optical filters of different colors. If blue and...

International Telecommunication Union

(Encyclopedia)International Telecommunication Union (ITU), specialized agency of the United Nations, with headquarters at Geneva. It was created in 1934 as a result of the merging of the International Telegraph Uni...