What is space junk and why is it a problem?
Space junk includes old inoperative satellites; pieces of old rockets that were jettisoned during launch, etc. They circulate around the earth, and there is danger of a spaceship or satellite colliding with one (even a piece of space junk a few centimetres in size could cause catastrophic damage). Also, if space junk is knocked our of its orbit (say, by collision with another piece), it could fall on earth and cause damage. Gradually over time, satellites’ orbits ‘degenerate’, and space junk will eventually fall to earth. it is better to plan when and where a piece of space junk falls, and sometimes they are deliberately caused to fall to earth (eg, the old space lab).
