No need to don a hard hat just yet. The odds that one of the millions of pieces of trash orbiting Earth will fall and hit you are about one in a trillion, says Bill Ailor, director of the Center for Orbital and Reentry Debris Studies.
The risk that someone will get hit can run far higher, though, says Nicholas Johnson, NASA's chief scientist for orbital debris. NASA and other space agencies aim to keep the risk of injury from falling objects lower than one in 10,000. The risks typically run higher with large objects. For example, there's a one-in-1,000 shot that the Hubble Space Telescope could hit someone if it falls from orbit once it's decommissioned, so NASA will preemptively steer it into the ocean.