October 4, 1957

IN THE WORLD

History changed on October 4, 1957, when the Soviet Union successfully launched Sputnik I. Sputnik 1 was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the USSR on 4 October 1957 as part of the Soviet space program. It was a polished metal sphere 23 inches in diameter with four external radio antennas to broadcast radio pulses. Its radio signal was easily detectable by radio amateurs, and the 65° orbital inclination and duration of its orbit made its flight path cover virtually the entire inhabited Earth. The satellite's unanticipated success precipitated the American Sputnik crisis and triggered the Space Race, part of the Cold War. The launch was the beginning of a new era of political, military, technological and scientific developments. Tracking and studying Sputnik 1 from Earth provided scientists with valuable information. The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave data about the ionosphere. It orbited for three weeks before its batteries died and then orbited silently for two months before it fell back into the atmosphere on 4 January 1958.