Another thing I dont understand about SR. Length contraction. As I move at near the speed of light, a stationary observer observes my length to be contracted. What exactly contracts? Is it the space between my molecules or the molecules themselves? Furthermore, if we switch perspective to my point of view and say the "stationary observer" is contracted in the opposite direction, how does that square with our two rulers. Mine is shorter than his from his perspective, and mine is longer than his from my perspective. How can this be?