What happens when space debris crashes on Earth?

China's Long March 5B rocket's core stage is set to make an uncontrolled reentry into Earth's atmosphere in the next few days. 

While the main stage released the Tianhe, or "Heavenly Harmony," module – the makings of the country's first permanent space station – shortly after the eight-minute mark of the mission, Gizmodo reported that the core stage stayed in space and did not perform a controlled deorbit.  Although rocket manufacturers typically take precautionary measures to avoid falling rocket debris, Inverse says the Long March 5B rocket stage is built without a steering booster, stabilization system and restartable engine.