I have this idea for a science fiction story (It actually came to me in a dream.). In the distant future, the inhabitants of the Milky Way have formed a galaxy-spanning civilization similar to the Republic in *Star Wars*. However, instead of using FTL starships to travel between planets in different star systems, they *move the planets*. Each member world has been outfitted with a powerful **jump drive** allowing it to travel thousands of light-years in the blink of an eye. It might work by temporarily enlarging microscopic primordial wormholes (Einstein-Rosen bridges) and "warping" through them, but that's just one option.

A planet will use its jump drive to teleport from its current star system to another one, where it will assume an orbit in its habitable zone. A given planet will undergo about 1 to 4 jumps per day, with each jump being planned weeks or months in advance. When two planets are in the same star system, people use sub-light starships to travel between them. After a ship makes the trip from one planet to another, it can land or it can enter orbit and "ride out" the next jump. Since there may be a dozen or so member worlds in a given star system at a given time, a single ship can reach any other member world within only a few jumps (Think Six Degrees of Kevin Bacon.).

My question is, how can I justify this system? What principles, based in real physics or sci-fi logic, can I use to explain why using a starship for FTL travel is impossible/more difficult/less efficient but using something as massive as a *planet* to do it is possible/less difficult/more efficient?

Keep in mind that FTL *communication* exists in this setting, and may use a technology similar to that of the planetary jump drives or something completely different.

Edit: I might call my story "The Planetary Exchange" as a parallel to the Stock Exchange. And the jumps would be coordinated via a central computer network; it wouldn't be a chaotic free-for-all.

Another Edit: Oh, and during a jump any moon(s) in orbit around a planet will also be taken along for the ride, not just starships.