## True Horizon and Linear Perspective

In graphical, linear perspective, the horizon is the horizontal line where the vanishing points for level objects lie. However, as the Earth is a sphere, the horizon of linear perspective is not the same as the true horizon, which is the line that we observe separating Earth from the sky.

Flat-Earthers claim that the observed horizon is produced by the law of perspective. In reality, from a high vantage point, we can try extending level and parallel lines to find their vanishing points. In many cases, they will end up above the true horizon.

## Flat-Earth “Perspective” is not Real-World Perspective

To an observer, the law of perspective will cause objects moving away in a straight line to:

1. appear to approach the vanishing point but never quite reach it,
2. never appear to go across the vanishing point,
3. appear to shrink in size,
4. never appear to be cut in half unless when it is obstructed by another object.

If the Earth were flat, sunsets, sunrises, and other general phenomena where objects are not visible due to Earth’s curvature should not occur. To “fix the problem,” flat-Earthers invented the explanation that the apparent obstruction of a distant object can occur on a flat Earth due to “perspective.” Their “perspective” is simply a baseless ad-hoc explanation that does not resemble how the real-world perspective works.

## Geometry of Perspective

Perspective is a relationship between the size of an object, its distance, and its apparent/angular size. The angular size is larger if the object is closer or larger.

Often, flat-Earthers would claim that we cannot see a distant object is not the result of Earth’s curvature, but because of perspective. In a way, it is correct to say that perspective might result in an object having angular size too small to be seen by our eyes. However, perspective alone cannot ‘hide’ a portion of an object, while revealing the rest of it.