I picture two reference frames for two different objects moving relative to each other as two coordinate spaces S and S'. My question is, say both spaces start of on top of each other (ie both objects are initially stationary) and then the objects start moving relative to each other, would the whole coordinate space for one of the objects move or do their origins always coincide and one just expands/shrink but remains centered on the origin? Is this a bad way to think of it? I've read my notes a few times but I'm still having a hard time trying to picture SR in my mind :(. Can anyone suggest any other ways to picture SR?