Length contraction happens only in direction of motion. Never perpendicular to the motion. My questions are 1) Why is it so?. For an observer in the same frame, it would mean a meter scale to give 2 different results. If by some means he is able to calculate the difference won't he be able to tell that he is in motion, thus violating POR? 2) What happens to the lengths neither perpendicular, nor parallel to the direction of motion?. Is the contraction according to trigonometry?