The launch of the basketball-size satellite is widely considered the dawn of the space age, and began the space race between the United States and the Soviet Union.
In 1955, both the United States and the Soviet Union announced plans to launch satellites into orbit as part of the International Geophysical Year, which had been established to take place from the middle of 1957 through the end of 1958.
The U.S. may have announced its plans first, but the U.S.S.R. got off the ground startlingly fast. Sputnik I, pictured at left, launched October 4, 1957, raising fears among Americans that it gave the Soviet Union a leg up on the U.S. not only technologically, but in the ability to launch nuclear missiles.
Sputnik II, carrying a dog named Laika and a much heavier payload, soon followed, launching only a month later on November 3.
Captions by CNET News.com's Jennifer Guevin
October 1, 2007 4:00 AM PDT
Photo by: NASA
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