Question

Define A horizon
send long answer​

Answer 1

The horizon or skyline is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. The true horizon is actually a theoretical line, which can only be observed when it lies on the sea surface.

Answer 2

The line or circle that forms the apperent boundary between earth and sky ....the small circle of the celestial sphere whose plane is tangent to the earth at the position of given observer, or the plane of such a circle. Also called rational horizon.