The core stage of a Long March 5B rocket is expected to slam into Earth's atmosphere Saturday (May 8) or thereabouts, although nobody can pinpoint the date, time or location yet. Such predictions can generally only be made just hours before impact, because atmospheric drag changes significantly as solar activity shifts.

Odds are the 23-ton (21 metric tons) piece of space debris will break apart high in the atmosphere and largely burn up, experts say, with any remaining pieces hitting uninhabited areas, as 70% of Earth's surface is covered in ocean. But again: We don't know that for sure.