Sputnik is the name for a series of artificial Earth satellites that were launched by the Soviet Union that began the Space Age. The first three were launched during the International Geophysical Year, a period lasting from July 1, 1957, to December 31, 1958. The Council of Scientific Unions encouraged space launches during this time because it was a period of peak solar activity.
Sputnik 1, a 184-pound (84-kilogram), 23-inch-diameter (58-centimeter) capsule, was launched on October 4, 1957, and took 96 minutes to circle the Earth. It remained in orbit for 57 days, when it reentered the Earth's atmosphere and burned up. This satellite was launched by a Soviet intercontinental ballistic missile. The launch vehicle had worrisome military implications for the United States because it could reach targets in the United States in less than an hour, much more quickly than a conventional bomber aircraft.
Sputnik 2, launched on November 3, 1957, carried the dog Laika, the first living creature to travel into space and orbit the Earth. The satellite weighed 1100 pounds (508 kilograms).
The launches of Sputnik 1 and Sputnik 2 led the United States to pursue its early space activities with more vigor and led to the creation of the National Aeronautics and Space Administration (NASA) in 1958. The United States launched its first successful satellite, Explorer 1, on January 31, 1958. It was much smaller than the Sputniks, weighing only 31 pounds (14 kilograms). The Soviets responded with the launch of Sputnik 3, a much heavier satellite that weighed more than a ton and was its first space laboratory, on May 15, 1958.
The country would launch seven more Sputnik satellites into 1961. These carried animals that were used to test spacecraft life-support and reentry systems and the space environment and also continued tests of Soviet rocket technology. These spacecraft weighed several tons and were precursors to the Vostok spacecraft that would carry Yuri Gagarin, the first human, into space in April 1961.