History changed on 4 October 1957, when the Soviet Union successfully launched Sputnik I. While the Sputnik launch was a single event, it marked the start of the Space Age and the space race between the USA and USSR.

Sputnik was the first artificial satellite to be put into geocentric orbit. The satellite helped to identify the density of high atmospheric layers by its orbit change and provided data on radio-signal distribution in the ionosphere.

The surprise launch of Sputnik 1 shocked the United States, which responded with a number of early satellite launches, including Explorer I, Project SCORE, Advanced Research Projects Agency and Courier 1B.

Sputnik also led indirectly to the creation of NASA and major increases in U.S. Government spending on scientific research and education.

Sputnik I was 58 cm in diameter and weighed approximately 83.6 kg. Each of its elliptical orbits around the Earth took about 96 minutes. Sputnik 2 was launched on 3 November 1957 and carried the first living passenger, a dog named Laika.

The first attempt to launch Sputnik 3, on 3 February 1958, failed, but the second on May 15 succeeded, and it carried a large array of instruments for geophysical research. Its tape recorder failed, however, making it unable to measure the Van Allen radiation belts.

Sputnik 4 was launched on 15 May 1960 and Sputnik 5 on 19 August 1960 with the dogs Belka and Strelka, 40 mice, 2 rats and a variety of plants on board. The spacecraft returned to Earth the next day and all animals were recovered safely.