This thread has devolved to a painful level. If you watched a 'sinking ship' to the point where all you saw was the mast, regardless of your world view, you would know you were seeing something beyond the horizon - whatever 'horizon' means in your world view. The boat's hull has disappeared behind it, but the mast is still visible, but since we know the mast is part of that boat we watched disappear, the mast is clearly beyond what we perceive as the horizon.
In RE we argue that it is the curved surface of the water that is obstructing view of the bottom of the boat, in FE, its perspective, attack angle, angular resolution, EA, a fat morgana - whatever.
I'm not sure how we got to the point where we're arguing about the definition of 'beyond'