I completely understand the effects of parallax as well as perspective...intuitively; but I can't seem to explain them to a particularly inquisitive child I'm tutoring. He wants to know, in conceptual terms, why objects in the distance like the moon seem to move in the same direction as you (the moon is following me!), while close objects seem to move in the opposite direction to one's movement. He also wants to know, again in conceptual terms, why things in the distance look smaller and why lines seem to converge. I told him it's because objects subtend a smaller angle the further away they are, but he wasn't satisfied with my admittedly under-thought answer. Any help in explaining and understanding this would be greatly appreciated. Thank you!