I'm going to word my point another way, then I'm going to leave it alone: the horizon
does appear to curve, if you have a wide enough expanse to look at. This curve gets easier to see the higher you go. This curve also
means precisely squat in the RE/FE debate. This curve would exist just as easily on a FE (provided there was something creating a horizon effect) as it does on a RE. The only thing this curve tells us, is that we are at the centre of our little personal bit of visible earth.
Let me say it one more time: A CURVED HORIZON MEANS NOTHING. The fact that there is a horizon at all, however, is something worth talking about.
Why is it that distant objects that are higher remain visible when objects at the same distance but lower appear to go behind this horizon?
Why does a ship appear to sink as it travels away?
Why does land appear to sink if you travel away from it on a ship?
Why, when traveling over land, do mountains disappear bottom first in the same manner?
Why, when I
measure the apparent height of a distant mountain, do my results indicate a round earth?