You obviously can’t see it when you gaze up at the night sky, but Earth has a whole lot of junk floating around in orbit. There are all kinds of reasons why debris ends up orbiting Earth and many of the objects are discarded pieces of other spacecraft or long-dead satellites which have no use to anyone. Sometimes these objects crash into each other and create even more, smaller pieces of space junk which can damage active satellites and even pose a danger to astronauts.