In The Voyage Home, Earth and four other human colonies have been removed from galactic maps. Approximate coordinates and an unexplained gravitational influence on nearby stars still allow Earth to be found. Reconnaissance then reveals four alien cruisers, ten frigates and a large orbital shipyard. The concentration of warships and construction facilities explains why the occupiers have concealed the system. It also forces the approaching ship to turn away before attempting a direct arrival.
Chapter · 3:09:43-3:10:33
Finding the hidden Earth in The Voyage Home
An occupied Earth can be erased from maps while remaining detectable through its gravitational effects and the military activity around it.