Vehicles disappearing over the horizon despite no curvature

Railroads show us how objects can disappear even though they are only 500 meters in the distance, this is due to diffraction caused by having a camera height of 2 centimeters (half the camera lense size) above the metal rail. This is similar in dimensions to having a viewer height of 2 meters over a distance of 50,000 meters. Like looking across Lake Ontario from the south shore to the Toronto skyline.