Sputnik was about the size of a basketball. It weighed only 83 kg (183 pounds).
Sputnik orbited the Earth every 98 minutes sending back a beeping signal for 23 days.
Sputnik's designer, Sergei Korolev (above), went on to head Russia's Vostok, Voskhod, Zond and Kosmos programs.
NASA was created as a direct result of the Sputnik surprise.