posted by parker .
on a lake without any waves, how far from the shore is a sailboat when the top of 10 m mast disappears from view of a person whose eye height is one m above the water's edge
The distance D to the horizon in km by an observer at H m from the ground is given approximately by
The visible distance between two objects at H1 and H2 away from (the same) horizon is thus given by the sum of the distances, namely:
Follow the derivation of the formula to understand the geometry behind it.