The universe, the world and the cycle of life. A cleaned up version of one of my comments.
Below is a comment I posted under 
The Comment:
There are a lot of things we have trust the theories that Scientists have arrived at, (and some evidence we can't wrap our heads around understanding,) I like how you started by the sphere/flat earth theory.
"'The world is spherical', so I heard... With lots of theories to back it up. Others believe the world to be flat, with theories to back it up."
I'm leaning toward believing that earth is a spherical planet, but who knows? Life has always thrown curveballs in scientists' theories and Laws. It reached a level where it's hard to make sense of what's happening.
Remember when The Theory of Relativity didn't exist? There are always abother layer science haven't reached yet. People don't need explanations to live their lives. Those of us who do are stupid, maybe in a good way.
As for the other interesting part in the article...
"You were born and therefore, you also will have to get married and have a family too."
One thing about the cycle of life I'd like to add, "it's instinctive." People want to marry and 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 sounds 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?" The manga starts by him falling in love with an android girl, only to realize she has shorter lifespan than him. It's was wholesome story even when you know you're on a time limit.
The world was a dystopia, but when he sees a recording from his parents, they talked about wanting to have him in that world, to experience joy, even in a dystopia. It moved him, and me as a reader. Sometimes, suffering is worth it.
Don't you think?
Salam (Peace)