Night and Day

In our reality built upon divisions, night and day are the very top of the mountain and the deepest inside the center of Earth.  Light and dark.  How does something so fundamental to our existence remain so unexplored?  There are some psychological implications explored in our waking versus dream state.  But to have scientifically and metaphysically ignored the fundamental purpose of the division between night and day means we have yet to really establish a culture and an ethos deeply founded upon our nature of half light and half dark.