Complex sentence: The world's first artificial satellite, Sputnik 1, had been put into orbit by the Soviet Union in 1957, and this could be considered the beginning of the Space Race between the Soviet Union and the United States.
Split into simpler sentences: The world's first artificial satellite, Sputnik 1, had been put into orbit by the Soviet Union in 1957. This event could be considered the beginning of the Space Race between the Soviet Union and the United States.