You're wasting your time here. I spent 38 years of my life believing in the same thing that you and most people continue to believe, and I'm done with that until some solid answers are provided. And these aren't the questions I'm asking. In fact, I'm not asking any questions here.

It's very simple. Let some flat earthers go to Antarctica and freely explore to put this all to bed. They will never allow that, so we're at an impasse of ideological beliefs.  

 Solid answer: Foucault Pendulum. 
Conclusion: can be observed.