The distance to the horizon depends primarily on the observer's height above ground level. For an average human standing on the Earth's surface (around 1.7 to 1.8 meters tall), the horizon is approximately 3 to 5 kilometers (about 3 miles) away. More precisely, the distance to the horizon can be calculated using the formula:
d=2Rh+h2d=\sqrt{2Rh+h^2}d=2Rh+h2
where ddd is the distance to the horizon, RRR is the Earth's radius (about 6,371 kilometers), and hhh is the observer's height above the surface in the same units. This means for a typical person standing on the ground, the horizon is around 4.7 to 5 kilometers away. If the observer is higher up, the horizon distance increases. For example, at a height of 10 meters, the horizon is roughly 11 kilometers away, and from the top of Mount Everest, the horizon can be about 370 kilometers away. In summary, the horizon for a person of average height standing on Earth is about 3 to 5 kilometers (roughly 3 miles) distant, and this distance grows with height following the geometric formula above.
