I quote: "Edit: before we look at the photos, I just want to clarify what this image actually shows, since there seems to be some confusion from both sides of the issue. At any altitude above the surface of a sphere, you are looking *down* at the horizon. Even when you are standing with your eyes six feet above the surface.
"People say “the horizon is flat and level,” and yes, that’s true, but it’s a flat, level *circle,* and that circle is NOT centered around your eyes, it’s centered roughly two feet below the surface you’re standing on. If you are looking at the horizon from a viewer height above sea level of six feet, then the horizon is 24 inches within the sphere under you, so you are eight feet ABOVE the center of the circle, and you SHOULD see curvature at the edge.
"Not curvature “down,” but the curvature at the edge of the circular horizon centered two feet below your shoes. And THAT’S what these two photos show!"