I recently read about this thing Galileo discovered with several experiments. Everything, with any mass, falls at the same speed, on the moon. Ok maybe... explanations always mention the missing air resistance and that two falling objects with different mass are attracted with the same gravity... I'm no expert. All the calculations seem right in any way, but I have a logical problem while thinking it through. Assumption: I have two cuboids, one made of solid steel, the other one is of hollow plastic. These two objects have the exact same dimensions. You can only differ them by lifting. Now, I drop them both from the same height on a flat surface. I assume that the heavy one hits the ground first. Is that the case because of density? If yes: If I resize/inflate the heavy cuboid to a height (same bottom dimensions as the other, that its air resistance during falling stays the same) where it has the same density as the lighter object (weight stays also the same), will they fall at the same speed now? Would they (same size and shape, different weight) hit the surface at the same time if I dropped them in a vacuum chamber?