Physics in the real world and physics in the Star Wars universe aren't the same.
Even ignoring The Force, several technologies necessary for cheap spaceflight (hyperspace engines, repulsor engines, etc) are described in a way which implies that they use little more than coils of electrified wire in order to function. In the real world, the best one could do with coils of wire is create magnetic fields, or electromagnetic waves, but in the Star Wars universe they produce very different effects.
Let us suppose that there existed, in the Star Wars Universe, some (unique) Machine, which altered the laws of physics in it's vicinity, producing what we think of as normal Earth physics.
This Machine has been active in our solar system for five or ten thousand years.
Some time prior to that, samples of human life were taken, and those samples in turn became the ancestors of humanity throughout the galaxy... then The Machine was turned on, to make Earth into a nature preserve of sorts.
Does this idea seem unreasonable? Is it conceivable for the laws of physics on earth and physics in the rest of the galaxy to be different?
If you're curious about the plot: Someone will smash The Machine in the prologue. Every running electric motor, dynamo, alternator or generator will come to a dramatic screeching halt, with sparks flying everywhere, and will not restart; motors and such which weren't running also will not operate properly, as they have in effect been transformed into (very inefficient) repulsors or hyperspace engines, etc.
There are of course numerous tragic deaths, but on the other hand, the destruction of The Machine sends out a signal which is heard throughout the galaxy, causing The Empire to investigate. Since Earth has no non-humans whatsoever, and The Empire thinks of themselves as the good guys, some sort of humanitarian effort begins.