physic question?

[jamiednae]

if you look carefully at a shadow, you will notice that it has a dark central region and a fuzzy and less dark band around the edge of the central region. why do shadows have two different regions?

[mrzwink]

because the source of light is never one single point.

this picture illustrates nicely with our solar system. but it really works for any source of light.
http://www.astro.oma.be/INFO/GIF/fig04.gif

light from one edge of the light source, cast one shadow.
light from the other edge of the light source also casts a shadow. both these shadows are quite weak, except in the part where they overlap.