The Space Age equivalent of dropping a house on a witch.
One of the most dramatic ways to try and bring about The End of the World as We Know It. Put simply, just set any sufficiently large object on a course toward the Earth, and make sure you're off-world when it hits. Or not, if you don't care about surviving it or you're already going to be dead when it happens.
The sky literally falling has [...] [tvtropes.org]