What's a Sputnik?
Before astronauts, space missions flew without a crew. The first of these, Sputnik, came from the Soviet Union. Sputnik technically wasn't a satellite, it was a 184-pound basketball-size bundle of radio transmitters that took only 98 minutes to orbit Earth. When it was launched on October 4, 1957, during the height of the Cold War, the United States was caught completely by surprise and the "Space Race" was on!
Discover even more highlights from 1957 as our list continues on the next page.