There are a lot of things we have trust the theories that Scientists have arrived at, (and some evidence we can't wrap our head around understanding,) I like how you started by the sphere/flat earth theory. I'm leaning toward believing that earth is a spherical planet, but who knows? Life has always thrown curveballs in scientists' theories and Laws.
Remember when The Theory of Relativity didn't exist? People don't need explanations to live their lives. Those of us who do are stupid, in a good way.
One thing about the cycle of life I'd like to add, "it's instinctive." People want to marry or have children, at least most of them have deep rooted desire for so, and would if the circumstances allow it, but we're living in an age that makes wanting that absurd. "Why would you bring a new child to a world that made you suffer and would make the baby too?"
I read a manga a long time ago that explored this idea, having the terminally ill main character always wondering "why he was born if only to suffer?" He fell in love with a girl only to realize she has less left in life than him. The world was a dystopia, but when he sees a recording from his mother and father, they talked about wanting to have him in that world, to experience joy, even in a dystopia.
^ I should clean this comment & turn it into a post.
!PIZZA !LUV