The space around our planet is not a desolate, empty place, it is filled with millions pieces of man-made debris from old rockets, abandoned satellites and missile shrapnel. In the sixties and seventies both the U.S. and the Soviet Union tested a lot of anti-satellite weapons, accidents with booster stages and satellites happen, and discarded bits left over from separations, frozen clouds of water and pieces of paint all remain in orbit.
Earth's orbit is segregated into three distinct regions:
The lower the orbit, the less time the object is likely to remain in space before returning to Earth. In the last five decades, an average of one piece of junk fell to the Earth each day. Most of it burns up in the atmosphere before it ever reaches the surface and nearly everything larger than 10 cm gets fragmented. Those that survive the entry, often fall into water, the ocean making up some 70 percent of the Earth's surface.