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Why does the edge of a shadow sometimes appear to shift when another shadow gets close to it?
Details: I was in front of a window. The edge of a chair cast a shadow on the floor from the window light. When I moved such that the shadow of my arm got very close to the shadow of the chair, part of the edge of the chair's shadow was "pulled towards" the shadow being cast by my arm. The shadow of my arms didn't appear to move. My arm was closer to the sun than the chair.
Interesting! I can see this happening when I wave my hand in front of my window. When the shadow of my hand gets too close to the shadow of my window frame, the shadow of my hand seems to elongate. The window frame is closer to the light than my arm is. It doesn't work if my hand is too close to the wall. It also seems to bend a little, depending on the angles; and if I have my fingers in a /\ shape and bring them together, I can make a shadow grow between them towards the tips, kind of like an A shape.
One thing I notice is that shadows don't have hard edg... (read more)