If Keiji is standing at the bottom of a well and looks up towards the sky, what shape does the visible sky take from his perspective? Respond very briefly.
The visible sky from Keiji's perspective takes the shape of a circle. When he looks up, he can only see the portion of the sky that aligns with the top opening of the well. From his viewpoint, the walls of the well block the rest of the sky, and so the sky appears as if it has the same circular shape as the well's opening. This is similar to looking through a tube or pipe; one can only see through the circular end, and the view is framed by its circular edges. Thus, Keiji sees a round section of the sky.