The answer to the question as to 'what is the purpose of day and night' is simple: 'God dreams itself into existence.' I have very lucid dreams about the underyling current of our reality in the early morning hours, usually about 4 or 5 am. As it was the case this morning when it all came to me. I understood the purpose/reason for day and night, or, the method how God dreams itself into existence. We are dreaming ourselves into existence. What it means is that our collective dreams lead to self-manifestation/self-materialization. One part of the world dreams while the other part is awake; a self-birthing process of sorts. It almost seems certain to me that the part that is asleep/dreaming (supports/helps to) manifests the part that is awake thus giving birth to its very own physical manifestation (in the understanding that the collective is one undifferentiated self; Oneself aka God). Sure; we can call it consciousness as in 'consciousness dreams itself into existence'. It is all G-d. The most simple conclusion: Self creates itself through the method of dreaming; night and day are complementary forces of self.
~ Wald Wassermann