This is the result of an ancient spitball and boredom. I noticed the spitball and got some double-stick tape and stuck two thumbtacks upside-down under it. But, I was very very very very bored. :P

Well, that's the HB point. If shadows are not parallel, then the light source must be close by (unless some claim that there are two sources of light, which is silly, since there is only one shadow per object). The Sun is not close by, so why do shadows diverge?

We all know it's perspective, but it does seem to throw people when they see it in pictures. I've given my Moon Hoax talk dozens of times, and the part about non-parallel shadows really gets them (I show an image of railroad tracks converging into the distance to drive the perspective point home). After I gave the talk in Sydney, we went outside and saw non-parallel shadows everywhere. It was fun.

I did that too after the Fox Show and it was a lot of fun. I still do it.

I use a variation of the railroad track idea. Instead of an image, I have someone draw it.