Sputnik, << SPUHT nihk, >> is the name of a series of unmanned satellites launched by the Soviet Union. Sputnik 1, launched Oct. 4, 1957, was the first artificial Earth satellite. It circled the Earth once every 96 minutes at a speed of 18,000 mph (29,000 kph), until it fell to Earth on Jan. 4, 1958. The Soviet Union also launched nine much larger sputniks, from November 1957 to March 1961. The earliest of these carried the first space traveler, the dog Laika . 
