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luminescence

(Encyclopedia)luminescence, general term applied to all forms of cool light, i.e., light emitted by sources other than a hot, incandescent body, such as a blackbody radiator. Luminescence is caused by the movement ...

melting point

(Encyclopedia)melting point, temperature at which a substance changes its state from solid to liquid. Under standard atmospheric pressure different pure crystalline solids will each melt at a different specific tem...

microphone

(Encyclopedia)microphone, device for converting sound into electrical energy, used in radio broadcasting, recording, and sound amplifying systems. Its basic component is a diaphragm that responds to the pressure or...

Aristide, Jean-Bertrand

(Encyclopedia)Aristide, Jean-Bertrand zhänˈ bĕrträndˈ äˌrēstēdˈ [key], 1953–, president of Haiti (1991, 1994–96, 2001–4). A radical Catholic priest who defended liberation theology, he worked among ...

Sagan, Carl Edward

(Encyclopedia)Sagan, Carl Edward sāˈgən [key], 1934–96, American astronomer and popularizer of science, b. New York City. Early in his career he investigated radio emissions from Venus and concluded that the c...

ballistics

(Encyclopedia)ballistics bəlĭsˈtĭks [key], science of projectiles. Interior ballistics deals with the propulsion and the motion of a projectile within a gun or firing device. Its problems include the ignition a...

Randolph, Edmund

(Encyclopedia)Randolph, Edmund, 1753–1813, American statesman, b. Williamsburg, Va.; nephew of Peyton Randolph. He studied law under his father, John Randolph, a Loyalist who went to England at the outbreak of th...

Timor

(Encyclopedia)Timor tēˈmôr [key] [Malay,=east], island (1990 est. pop. 3,900,000), c.13,200 sq mi/34,200 sq km, largest and easternmost of the Lesser Sundas, in the Malay Archipelago. Timor is divided politicall...

vibration

(Encyclopedia)vibration, in physics, commonly an oscillatory motion—a movement first in one direction and then back again in the opposite direction. It is exhibited, for example, by a swinging pendulum, by the pr...

shock absorber

(Encyclopedia)shock absorber, device for reducing the effect of a sudden shock by the dissipation of the shock's energy. On an automobile, springs and shock absorbers are mounted between the wheels and the frame. W...