It sounds funny but trash is space is decidedly deadly. Of the 20,000 objects we have in orbit, 95% are dead or debris. Old satellites can be commanded to dive into the atmosphere and burn up or sent into orbits that hopefully keep them out of the way of the 19,999 other objects; but mistakes and mishaps happen. Collisions disable satellites and create more debris that can create more collisions. Considering the orbital speeds, collisions can happen at several kilometers per second; basically, thousands of uncontrolled bullets shooting past equipment that is vital for running our civilization and monitoring our terrestrial and planetary environment. One great fear is a great cascade of collisions that effectively knock out most of the satellites and create thousands more pieces of debris creating a shell of dangerous debris. It isn’t easy cleaning up that many bullets of various sizes and orbits. Proper design and collaborative traffic control help, but until a clean-up campaign succeeds we live with the threat of losing a resource vital to our current way of life.