The horizon isn't something that was "invented". It's a natural phenomenon that arises from the curvature of the Earth and our perspective as observers on its surface.

Here's a breakdown:

* Earth's Curvature: The Earth is a sphere, not flat. This curvature means that the Earth's surface curves away from you as you look out.

* Line of Sight: Our vision travels in straight lines.

* Horizon Formation: The horizon is the point where the Earth's surface appears to meet the sky. Because of the Earth's curvature, this line of sight intersects the surface at a distance, creating the illusion of a horizontal line.

So, the horizon isn't an invention. It's a consequence of the Earth's shape and our perception of it.