## Magnitude of Visible Earth’s Curvature in a Photograph

The magnitude of the curvature that appears in a photograph of Earth’s curvature depends on several factors:

1. The observer’s altitude.
2. The camera’s field of view or focal length.
3. The distortion characteristics of the camera lens.

Flat-Earthers like to dismiss a photo of Earth’s curvature by comparing it to another photo showing a different amount of curvature. In reality, to compare the visible curvature, we need to ensure all the images were taken from the same altitude, same field of view, and account for the lens’ distortion.

## Climbing Higher Reveals Distant Objects

Because the Earth is a sphere, the surface of Earth obstructs distant enough objects. Climbing to a higher altitude allows us to see farther and more of the previously obstructed objects will become visible, starting from the tops first.

This phenomenon would not occur if the Earth were flat. In a flat Earth, it would not be possible for Earth’s surface to obstruct more of an object —starting from the bottom portions first— if the observer is closer to the surface.

The same thing also happens for objects nearby a large body of water. The surface of the water —which is obviously lower than the object— can obscure the object if the viewer is far enough. Flat-Earthers often invent the “explanation” that Earth’s contour causes the obstruction. This phenomenon can easily prove them wrong.

## Level, Higher and Lower

A higher position is farther up, away from the center of the Earth, relative to sea level. Conversely, a lower position is closer toward Earth’s center, relative to sea level. Two positions are level if they are at the same height from sea level.

Some flat-Earthers are unable to understand this. To them, ‘level’ means straight. They are wrong. In Earth sciences, height is measured from a plane of reference, usually the sea level.