Sputnik 1

Sputnik 1 was the first artificial Earth satellite, launched by the Soviet Union on October 4, 1957. It was a 58-centimeter polished metal sphere with four external radio antennas to broadcast radio pulses. The mission was a surprise success that precipitated the American Sputnik crisis and triggered the Space Race, a central part of the Cold War. The satellite provided scientists with valuable information about the density of the upper atmosphere through its orbital decay and data on the ionosphere via its radio signals. Sputnik 1 orbited the Earth for three months until its batteries ran out, after which it continued to orbit silently before finally burning up in the atmosphere on January 4, 1958.