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reconnaissance satellite

(Encyclopedia)reconnaissance satellite, artificial satellite launched by a country to provide intelligence information on the military activities of foreign countries. There are four major types. Early-warning sate...

gyroscope

(Encyclopedia)CE5 Three-frame gyroscope gyroscope jīˈrəskōpˌ [key], symmetrical mass, usually a wheel, mounted so that it can spin about an axis in any direction. When spinning, the gyroscope has special p...

weather balloon

(Encyclopedia)weather balloon, balloon used in the measurement and evaluation of mostly upper atmospheric conditions (see atmosphere). Information may be gathered during the vertical ascent of the balloon through t...

sun, in astronomy

(Encyclopedia)CE5 Structure of the sun sun, intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the sola...

Garrison Dam

(Encyclopedia)Garrison Dam, c.11,300 ft (3,400 m) long and 210 ft (64 m) high, on the Missouri River, near Riverdale, W central N.Dak.; one of the world's largest earth-filled dams used for irrigation power. Built ...

Astraea

(Encyclopedia)Astraea ăstrēˈə [key], in Greek religion and mythology, goddess of justice; daughter of Zeus and Themis. Because of the wickedness of man, she withdrew from the earth at the end of the Golden Age ...

astronomical unit

(Encyclopedia)astronomical unit (AU), mean distance between the earth and sun; one AU is c.92,960,000 mi (149,604,970 km). The astronomical unit is the principal unit of measurement within the solar system, e.g., M...

Ymir

(Encyclopedia)Ymir ēˈmĕr [key], in Norse mythology, primeval giant and progenitor of a race of giants. Odin and his brothers slew Ymir; from his skull they fashioned the sky, from his flesh the earth, from his b...

Boisbaudran, Paul Émile Lecoq de

(Encyclopedia)Boisbaudran, Paul Émile Lecoq de pôl āmēlˈ ləkôkˈ də bwäbōdräNˈ [key], 1838–1912, French discoverer of the elements gallium, samarium, and dysprosium. He also made contributions in the ...

Joel, book of the Bible

(Encyclopedia)Joel, prophetic book of the Bible. It is a collection of the oracles of an otherwise unknown prophet, dated variously from the 9th to the 3d cent. b.c., though a date in c.400 b.c. is likely. A locust...