We can see the proof of a sphere Earth at least twice a day. Just go watch sunrise and sunset. Thanks for the sun being such a large object, we can see it rises from behind the horizon slowly and clearly. Unlike looking at a boat near the horizon being very blurry, Sunset and sunrise are very clear. We can see it being totally behind the Horizon to all the way up in the sky. You just can't say there is an optical illusion happening right there. You can even use a camera to zoom in and it won't make a difference.
