When we look at the horizon from the surface of the Earth, it looks perfectly flat, therefore we can certainly deduce that the Earth is not a small ball. But does this prove that the Earth is completely flat on the big scale?

If you look at a small circle, you will see a sharp curvature, but if you see a big circle, for example a circular building or a park, the edges will look almost flat. The bigger is the diameter, the more flat the curve appears. And when we get a bigger and bigger circle (or a sphere), it comes to a point where the curvature becomes unrecognizable. At that point **we are not expected to see the curvature**.

Earth is so big (12 000 km wide) that we cannot see the curvature. Even airplanes are not flying high enough (10 km high) to show a clear curve. The Earth is too big and we are too small. And it’s not easy to get far away from Earth enough to see a clear curve. Therefore **it is not smart to “debunk” globe by showing the flatness of the horizon in photos made close to Earth’s surface**. But it is smart to show the pictures from space to prove that the Earth is a globe.