>>16980731first of all, the "curve" was visible even on lower elevation. It's due to the camera. And you don't have a vertical arc in front of your eye level view if you were truly above a ball.
Complete the curve. What happens when it turns around 180 degrees? It would just see nothing. You wouldn't have the very same vertical arc in your field of view, which means it's just the optics of the camera that creates this arc. That horizon is all around the camera's eye level, 360 degrees, all on the very same elevation. The "curve" even changes, because again, it's just the camera's optics and not an actual physical earth curve.
