Sputnik 1 was the first artificial satellite launched into Earth orbit, on 4 October 1957.
The Soviet spacecraft was a polished aluminum sphere about 58 centimeters wide, with four radio antennas. Its beeping signals could be received by radio operators around the world, making the achievement highly visible during the Cold War Space Race.
Sputnik 1 was launched from the Baikonur launch site aboard an R-7 rocket. It transmitted for about three weeks before its batteries were exhausted, then continued orbiting silently until atmospheric drag destroyed it on 4 January 1958.
A common mix-up is confusing Sputnik 1 with Explorer 1, which was the first United States satellite. Explorer 1 launched in January 1958 and helped discover the Van Allen radiation belts.