Planet Drift is the theory that planets can be flung into the depths of a universe away from its originating star.
When stars lose their gravity hold over a planet, planets can be "released" into the universe, with the planet becoming its own little island in the middle of the universe. This typically means doom for the planet as it cannot receive any warmth from a sun. A Drifting Planet may one day be caught by another star, but it may take a very long time.
Humans are able to replicate Planet Drift by pushing planets or celestial bodies out of the gravity field it is in.