(IGY), 18-month period from July, 1957, through Dec., 1958, during a period of maximum sunspot activity, designated for cooperative study of the solar-terrestrial environment by the scientists of 67 nations. The only prior combined international scientific efforts took place during the Polar Years of 1882 and 1932. Discoveries were made in the fields of cosmic ray research, climatology, oceanography, and the nature of the earth's atmosphere and magnetic field. Earth satellites (see satellite, artificial) launched by the United States discovered the Van Allen radiation belts, the influx of charged solar particles detected believed to be responsible for northern and southern polar auroras. Soundings of the world's oceans revealed new information about the physical features on the ocean floor. Seismically active rifts along the summits of mid-oceanic ridges were identified. IGY scientists conducted extensive studies of deep ocean currents and developed better gravity measurements for mineral exploration. The major programs of IGY were continued from Jan., 1958, to Jan., 1959, as the International Geophysical Cooperation. Also connected to IGY was the International Years of the Quiet Sun, an international cooperative program during 1964 to 1965, that focused on solar-terrestrial phenomena during a quiet sun, or near sunspot minimum. The IGY was the largest and most important international scientific effort to that date. One of its many later ramifications was the setting aside of Antarctica as a nonmilitary region to be used for international scientific purposes alone. Antarctica has become a base for collecting meteorological data, including information on the presence and effects of moisture, carbon dioxide, and electrified particles on the atmosphere, and the general circulation of the atmosphere.

See S. Chapman, IGY: Year of Discovery (1960); W. Sullivan, Assault on the Unknown (1961); J. T. Wilson, IGY: The Year of the New Moons (1961).

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