If you have your leg in one position, it takes up a certain amount of space, right? So if you move your leg then you occupy a different area of space, and that previous area of space that your leg was in before now becomes vacant. This will apply to anything so long as you move something from one spot to the other so the previous spot is now empty. However, you come across a situation where you inhabit another area of space WITHOUT moving it previously and thus leaving the previous area of space empty then you are taking up space that isn’t there. This can occur if this something either shrinks or gets larger. But, if you are taking up space that isn’t there and thus moving space, or ‘packing it together’ then somewhere, some area of space is shifting. am i making sense?