text: how can gravity exist in the space ships in star wars?   presuming you mean real space ships operating in a zero-gravity environment and not just fake spaceships on a film set?  funkymonk is right, gentle accelleration followed by a turn-over mid trip and an equal dceleration would create a sensation of 'gravity' through the soles of the feet.  alternatively, in (say) a orbital space station, the interplay of centripetal and centrifugal forces created by spinning a structure, with its occupants, about its axis much like in the opening sequences of the film 2001, will create a sensation of gravity (tricky concept, very hard to understand ... serious maths involved) .  a large diameter structure spinning slowly would produce the best effect.  muscle wasting resulting from long periods in zero gravity is a major impediment to long space journeys, the gravity problem is one that needs to be resolved so that cosmonaughts can survive back in earth gravity once they return.