The U.S. Air Force estimates that 9,000 pieces of space junk larger than ten centimeters across are currently orbiting the Earth with thousands of more smaller pieces.
Space junk has only scored one confirmed hit on an active spacecraft.
In 1996 a French military satellite was hit and knocked into a new orbit.
The international space station has been forced to take evasive action on three occasions.
Vanguard 1, a U.S. satellite launched in 1958, is the oldest piece of space junk still up there.
Space junk is anything in space that is created by humans but no longer serve any useful purpose.