srh

Oh well...at least they used a real problem, with a real solution. I've seen too many movies where they attempt to make a maths related problem look amazingly complicated by writing random symbols and values on a blackboard that makes no sense whatsoever...or maybe it does, and I don't understand it, but by the placement of symbols etc, I doubt it.

I would think of a shadow as a volume, for convenience. I can see how it could be viewed as 2D, if you thought of it as just the outline on the ground, however a shadow, by your definition (depravity of photons), begins at the object which is causing the light to be blocked. So that would mean it starts at the object, traces out the objects shape through the air, until it hits another solid object, where it becomes most visible as the outline you see.

I?ve noticed this sort of behaviour particularly in children. When they fall off their bike, or fall over walking, running etc, besides recovering from the shock that the ground just jumped up and attacked them, they generally seem fairly calm. Most of the time they even stand back up, and it?s not until they notice the graze on their knee that they go off like a siren. There would have to be studies or articles on this apparent link between visual stimulus and the communication of pain to the brain?