Along time ago before the invention of electric lighting, our bodies use this method to allow us to stay awake when the Sun was out and allow us to feel tired and rest when the Sun went down.
I had the inspiration for my project when one of my friends in the Philippines told me that she failed her grade in school because she couldn't afford electricity. She didn't have any light to study with at night.
Cool, now I can be a third wheel on dinners with my crush. Oh wow, she's perfect, huh? You've never seen someone with better hair? Really, never? That's so funny. I object to this.