October 4 was the anniversary of 55 Years of Space Exploration. At the same day in 1957 the Soviet Union launched the first satellite, Sputnik-1, into orbit. This video, after the jump, is a celebration of 55 years of successful missions. Sputnik 2: Laika first animal in orbit, November 3, 1957.
Sputnik 1 was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957. The surprise success precipitated the American Sputnik crisis, began the Space Age and triggered the Space Race, a part of the larger Cold War. The launch ushered in new political, military, technological, and scientific developments.
Sputnik was also scientifically valuable. The density of the upper atmosphere could be deduced from its dragon the orbit, and the propagation of its radio signals gave information about the ionosphere.
Sputnik 1. Image credit Wikimedia