Glen,
If you mean the original Trilogy, (or Parts 4, 5, and 6) then the answer lies somewhere in the deep recesses of George Lucas' head!
Or, to put it bluntly....
....We don't bloody know!!!!!!
Ditto, for all of the Star Trek movies, the Indiana Jones series, etc, etc, etc.
Apologies if that sounds rude, but if we all had a penny for everyone who asked this question, we'd all be very, very rich by know!
Pooch