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International Geophysical Year
(Encyclopedia)International Geophysical Year (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 enviro...Geophysical Year, International
(Encyclopedia)Geophysical Year, International: see International Geophysical Year. ...Five-Year Plan
(Encyclopedia)Five-Year Plan, Soviet economic practice of planning to augment agricultural and industrial output by designated quotas for a limited period of usually five years. Nations other than the former USSR a...New Year's Day
(Encyclopedia)New Year's Day, among ancient peoples the first day of the year frequently corresponded to the vernal or autumnal equinox, or to the summer or winter solstice. In the Middle Ages it was celebrated amo...Year 2000 problem
(Encyclopedia)Year 2000 problem, Y2K problem, or millennium bug, in computer science, a design flaw in the hardware or software of a computer that caused erroneous results when working with dates beyond Dec. 31, 1...seventeen-year locust
(Encyclopedia)seventeen-year locust: see cicada. ...cycle
(Encyclopedia)cycle, in astronomy, period of time required for the recurrence of some celestial event. The length of a cycle may be measured relative to the sun or to the fixed stars (see sidereal time). A frequent...day
(Encyclopedia)day, period of time for the earth to rotate once on its axis. The ordinary day, or solar day, is measured relative to the sun, being the time between successive passages of the sun over a stationary o...synodic period
(Encyclopedia)synodic period sĭnŏdˈĭk [key], in astronomy, length of time during which a body in the solar system makes one orbit of the sun relative to the earth, i.e., returns to the same elongation. Because ...hour angle
(Encyclopedia)hour angle, in astronomy, a coordinate in the equatorial coordinate system. The hour angle of a celestial body is the angular distance, expressed in hours, minutes, and seconds (one hour equals 15 deg...Browse by Subject
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