Asked by: Anonymous
The horizon isn’t a static property of the Earth, like the equator or the North Pole. It’s an entirely local phenomenon that depends on the shape of the surrounding terrain, the atmospheric conditions and the height of your viewpoint. At the base of a cliff, or on a foggy beach, the horizon is technically just a few metres away.
Nevertheless, if you assume very flat terrain and good visibility, you can multiply your height in metres above the ground by 13, and take the square root of that. This is the distance to the horizon, in kilometres. That’s 4.8km for a person of average height standing at sea level and looking out to sea. From five metres higher up, at the top of the beach, the horizon would be almost twice as far away.