Can a shadow be measured for thickness

[hattster]

Does a shadow have a depth or thicknes to it, if so can it be measured

[jake-the-peg]

No a shadow is an area of an object that is illuminated with a lower level of light than its surroundings

[bernardo]

A shadow is not an area but a volume.  It extends all the way from the object or person who is casting the shadow, indfinitely far in space until it hits a surface on which to land.

[Calvesy]

From a point source of light, a shadow is an infinitely expanding cone unless it is cast upon an opaque obstruction. If the source of light is large, this umbra is surrounded by a penumbra which tapers the umbra to a point. This is why the area in which you can observe an eclipse is smaller than the moon, although the partial eclipse region (penumbra) is three times wider than the moon.

[jake-the-peg]

A shadow is generally taken to be the effect of the  relative absence of light in incidence with an object.

I call as my first witness http://dictionary.reference.com/search?q=shadow

Although scientifically we may have expanded the meaning I thing given the context of Hatsters other question about "what is darkness" we can assume the meaning of the question was based around this interpretation.

If we're being picky, can you have a cone of a lack of something?

Is that not a bit like a bottle of vacuum? :c)