Well if you look at it in the overall, there's a light source coming from the upper left from your perspective (i.e. in the room with you), the light hits the top metal bit more intensely than the bottom one but because of its angle the shadow would not be as deep as the lower metal bit. Imagine the sun directly overhead, you'd have no shadow, but an object that's to your right and south several hundred miles away would have a longer shadow. Um, at least that's my story and I'm sticking to it. LOL.