Since light is the basic physical manifestation of life, bathing all creation in its radiance, it is highly important to realize, in part at least, the subtle nature of this divine substance. That which is called light is actually a rate of vibration causing certain reactions upon the optic nerve. Few realize how they are walled in by the limitations of the sense perceptions. Not only is there a great deal more to light than anyone has ever seen but there are also unknown forms of light which no optical equipment will ever register. There are unnumbered colors which cannot be seen, as well as sounds which cannot be heard, odors which cannot be smelt, flavors which cannot be tasted, and substances which cannot be felt. Man is thus surrounded by a supersensible universe of which he knows nothing because the centers of sense perception within himself have not been developed sufficiently to respond to the subtler rates of vibration of which that universe is composed.
See also: The Sun