Most people believe length contraction is a real spatial phenomenon and if so there's nothing to contract in empty space and since matter contains mostly empty space then it is only the structure of matter that is physically contracting.
So now, if a mirror is mounted on a 45 degree plank coming out of the wall, only the plank and mirror will thin in the direction of motion when observed externally. The angle of the mirror won't change because there's nothing to contract irregularly behind the mirror. But if you mount the mirror on an L-bracket, the bottom of the bracket will contract more than the top and hence the angle of the mirror will now change solely because of the fact you've added matter to the bottom? Is this really how length contraction would work? Is this why pulses of light don't look contracted to us as they travel because they have no material structure to contract?