Read Strugatsky "The inhabited island". (I immediately warn you that until the hands of the screenwriters touched it, the thing was remarkable) So, there, the inhabitants of the planet Saraksha were convinced that they live on the inner surface of the ball. Only they logic a little "corrected".
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I also immediately remembered Strugatsky ("The refraction here, however, is monstrous!"). I could never have imagined such an atmosphere with a suitable air for a person... It’s all fantastic. So the curvature of the line of the horizon is not such a bad argument, for the Orthodox will come down (those hardly read the "Godmother" fantasy) ;)
Z is. In Saraksha, the concept of the form of peace was contradicted by ballistics (which did not prevent the military from believing in the World Light, and shooting "out of the horizon"). On Earth, ballistics confirms the concept. For believers, however, there is no proof of the error of their faith by definition.