The visible boundary, a perceptual line, occurs due to the curvature of the earth and atmospheric conditions. This apparent intersection gives the illusion of the celestial dome and terrestrial surface converging. A clear illustration is the unobstructed ocean horizon, where the air appears to touch the water at a distant point.
This visual phenomenon holds significance in navigation, art, and philosophy. Historically, observing this delineation aided seafaring and terrestrial wayfinding. It also provided inspiration for artistic expression and contemplation regarding humanity’s place within the broader cosmos, driving exploration and discovery. The concept also influenced landscape architecture and design, emphasizing openness and perspective.