On a ruler, you could move from the 1cm marking on a ruler to the 2cm marking, or you could move from the 0.5cm marking to the 1.5cm marking - both are 1cm movements but you cannot go from 1.5cm to 1cm in a 1cm movement. If we had Planck co-ordinates, could you move from 1 => 2 and also 1.5 => 2.5, and from 1 => 1.5? Also, in a hypothetical world where all movement occurs by contact alone, suppose we have two perfectly smooth flat planes, and no "action at a distance" in any way, separated exactly by 1 planck length. Could these plates collide? In other words - is space continuous but appears discrete when probed, or is it absolutely discrete?