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sunspots

(Encyclopedia)sunspots, dark, usually irregularly shaped spots on the sun's surface that are actually solar magnetic storms. The spots are darker because the temperature of the spots is lower than that of the surro...

quantum theory

(Encyclopedia)quantum theory, modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity togethe...

information theory

(Encyclopedia)information theory or communication theory, mathematical theory formulated principally by the American scientist Claude E. Shannon to explain aspects and problems of information and communication. Whi...

Mound Builders

(Encyclopedia)Mound Builders, in North American archaeology, name given to those people who built mounds in a large area from the Great Lakes to the Gulf of Mexico and from the Mississippi River to the Appalachian ...

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 ...

birth

(Encyclopedia)birth or labor, delivery of the fetus by the viviparous mammal. Birth is also known as parturition. Human birth normally occurs about 280 days after onset of the last menstrual period before conceptio...

broadcasting

(Encyclopedia)broadcasting, transmission, usually using radio frequencies, of sound or images to a large number of radio or television receivers. In the United States the first regularly scheduled radio broadcasts ...

pregnancy

(Encyclopedia)pregnancy, period of time between fertilization of the ovum (conception) and birth, during which mammals carry their developing young in the uterus (see embryo). The average duration of pregnancy in h...

infrared astronomy

(Encyclopedia)infrared astronomy, study of celestial objects by means of the infrared radiation they emit, in the wavelength range from about 1 micrometer to about 1 millimeter. All objects, from trees and building...

Holocaust

(Encyclopedia)Holocaust hŏlˈəkôstˌ, hōˈlə– [key], name given to the period of persecution and extermination of European Jews by Nazi Germany. Romani (Gypsies), homosexuals, Jehovah's Witnesses, the disabl...