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mass-luminosity relation

(Encyclopedia)mass-luminosity relation, in astronomy, law stating that the luminosity of a star is proportional to some power of the mass of the star. More massive stars are in general more luminous. For stars on t...

center of mass

(Encyclopedia)center of mass, the point at which all the mass of a body may be considered to be concentrated in analyzing its motion. The center of mass of a sphere of uniform density coincides with the center of t...

air traffic control

(Encyclopedia)air traffic control, the system by which airplanes are safely routed into and out of major airports. Air traffic control in the United States is centered in a number of regional control centers that r...

Strategic Air Command

(Encyclopedia)Strategic Air Command (SAC), former command of the U.S. air force (see Air Force, United States Department of the) charged with organizing, training, equipping, administering, and preparing strategic ...

air-cushion vehicle

(Encyclopedia)CE5 Air-cushion vehicle: In vehicles modified with a trunk or skirt (A), the rate of leakage is reduced and less power is needed to maintain the cushion. Vehicles designed to travel over deep water...

humidity

(Encyclopedia)humidity, moisture content of the atmosphere, a primary element of climate. Humidity measurements include absolute humidity, the mass of water vapor per unit volume of natural air; relative humidity (...

Langley Air Force Base

(Encyclopedia)Langley Air Force Base, U.S. military installation, 3,195 acres (1,293 hectares), SE Va., N of Hampton; est. 1917 and named for aviation pioneer Samuel P. Langley, amalgamated 2010 with Fort Eustis in...

Lackland Air Force Base

(Encyclopedia)Lackland Air Force Base lăkˈlənd [key], U.S. military installation, c.6,835 acres (2,766 hectares), S Tex., W of San Antonio; est. 1941, amalgated 2010 with Fort Sam Houston and Randolph Air Force ...

Malmstrom Air Force Base

(Encyclopedia)Malmstrom Air Force Base mälmˈstrəm, mălmˈ– [key], U.S. military installation, 3,573 acres (1,446 hectares), W central Mont., E of Great Falls; est. 1942. During World War II, it was the takeof...

Andrews Air Force Base

(Encyclopedia)Andrews Air Force Base: see Joint Base Andrews. ...