Due to the defect of human eyes,we are blessed to see a peculiarity in
the dimension of an object(opaque) and its shadow.We had seen the
shadows of many objects,but had you noticed any specialities?
Let me explain.
What is the shadow of a cubical box? a square.right? or a planar one.Okay?
Now whats the shadow of a squre lamina? or a bangle? a closed
string.Right? that is a closed line segment.
That is a 3-Dimensional object has a 2-Dimensional shadow,a
2-Dimensional shadow has a 1-Dimensional shadow and so on.That is if
the dimension of a body is 'n',the dimension of its shadow is'n-1'
So the 4-Dimension object must have a 3-Dimensional shadow.Even we
cannot give a perfect example there are still some indirect examples
which resemples their example.
1) Image of Rainbow in sky.
2) 3-D images created by interference and superpositioning of light
rays (laser shows).
3) Invisiblity of objects(air,water,glass etc...) even there are no
absolute black bodies in universe.