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air embolism

(Encyclopedia)air embolism: see embolus.

air forces

(Encyclopedia)air forces, those portions of a nation's military organization employing heavier-than-air aircraft for reconnaissance, support of ground troops, aerial combat, and bombing of enemy lines of communicat...

air lock

(Encyclopedia)air lock, compartment connecting two different environments, usually at different pressures, that enables personnel to transfer from one environment to the other. Space capsules have air locks to enab...

Aïr Massif

(Encyclopedia)Aïr Massif or Aïr Mountains, Africa: see Sahara. ...

air navigation

(Encyclopedia)air navigation, science and technology of determining the position of an aircraft with respect to the surface of the earth and accurately maintaining a desired course (see navigation). Basic to air ...

air plant

(Encyclopedia)air plant: see epiphyte.

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...

atomic mass unit

(Encyclopedia)atomic mass unit or amu, in chemistry and physics, unit defined as exactly 1⁄12 the mass of an atom of carbon-12, the isotope of carbon with six protons and six neutrons in its nucleus. One amu is e...

Mass, in Christianity

(Encyclopedia)Mass, religious service of the Roman Catholic Church, which has as its central act the performance of the sacrament of the Eucharist. It is based on the ancient Latin liturgy of the city of Rome, now ...

mass, in physics

(Encyclopedia)mass, in physics, the quantity of matter in a body regardless of its volume or of any forces acting on it. The term should not be confused with weight, which is the measure of the force of gravity (se...