If I say something's clearly visible to me and the reason you can't see something is probably because of poor vision, just saying the words "none was detected", i.e. repeating the fact that you can't see the thing, doesn't refute me.
Oh gee I wonder how a tower built to shoot a directional beam of light over the horizon to be easily spotted by passing ships might be spotted from a ship that's over the horizon?
And how could a force that affects objects in proportion to their mass possibly have so small an effect on creatures whose mass is very small?
RE: Question : At what height do we see curvature