All things were made by him; and without him was not any thing made that was made.
In Him was life; and the life was the light of men.
And the light shineth in darkness; and the darkness comprehended it not.


God is Light.  Quantum physics tells us the material universe is a hologram; a 3-d photograph made with light. 
The true Light of God is spiritual.  It is not visible to the physical eyes, only to the eyes of the soul.  Dark beings and dark people do not see it.  Some dark people sense it's presence and are attracted to sources of it, but they can't actually see it so they don't comprehend it.