Sputnik 1
1957
The first artificial satellite. A polished 58 cm aluminium sphere with four long antennas, launched by the Soviet Union on 4 October 1957.
Specs
Mass 83.6 kg; 58 cm diameter; 20 W radio beacon; ~92-96 min orbit; completed 1,440 orbits in 21 days; re-entered 4 Jan 1958.
Why it matters
It proved objects can be put into orbit around Earth - the first step of every card in this list. Its radio beep was heard by amateur radio operators all over the world: orbiting Earth was no longer theoretical.