Sonic boom

A sonic boom is a burst of sonic disruption that usually occurs when something large breaks hits a planets atmosphere. This was the case when the Sycorax ship entered Earth's atmosphere. The wave stretched on for miles with London as the epicentre. Glass windows all over the surrounding area were blown apart by the force of the blast. The same thing did not happen when the spaceship left the atmosphere, possibly because it was destroyed moments after. (DW: The Christmas Invasion)