For a few hours Monday, a nearly 20-ton piece of space debris fell uncontrolled from the sky, passing over Los Angeles and New York City and causing a bit of stress for the experts tracking it before it safely splashed down in the Atlantic Ocean. "The problem is that it is traveling very fast horizontally through the atmosphere and it’s hard to predict when it will finally come down," one astronomer explains to CNN. The empty core stage from China's Long March-5B rocket, which was launched last week and orbited for several days before re-entering Earth's atmosphere, is the fourth-largest piece of space debris ever to fall back to Earth uncontrolled, and the largest to do so since 1991, KTLA reports.
Had the Atlantic Ocean not ended up as the final resting place, however, the astronomer says things might not have turned out as poorly as you might be picturing. "For a large object like this, dense pieces like parts of the rocket engines could survive re-entry and crash to Earth," he says. "Once they reach the lower atmosphere they are traveling relatively slowly, so worst case is they could take out a house." SpaceTrack had pegged the US, Australia, and Africa as potential re-entry locations, and the debris ended up landing just off the coast of West Africa. ScienceAlert reports that the core stage of the rocket was 98 feet long, but SpaceFlightNow notes that most of the rocket was expected to burn up upon re-entering the atmosphere. (Read more space debris stories.)