If you?ve been next to a port lately, or just strolled down a beach and stared off vacantly into the horizon, you might have, perhaps, noticed a very interesting phenomenon: approaching ships do not just ?appear? out of the horizon (like they should have if the world was flat), but rather emerge from beneath the sea.
But - you say - ships do not submerge and rise up again as they approach our view (except in ?Pirates of the Caribbean?, but we are hereby assuming that was a fictitious movie). The reason ships appear as if they ?emerge from the waves? is because the world is not flat: it?s round.
Imagine an ant walking along the surface of an orange, into your field of view. If you look at the orange ?head on?, you will see the ant?s body slowly rising up from the ?horizon?, because of the curvature of the Orange. If you would do that experiment with a long road, the effect would have changed: The ant would have slowly ?materialized? into view, depending on how sharp your vision is.