How far away is the horizon at sea level?

Question

How far away is the horizon at sea level?

Answer 1

approximately 7 miles

Answer 2

the distance the eye can see to the horizon is the square root of the product of the elevation of the eye and the diameter of the Earth. So, if the elevation of the eye is 1.75 metres and the diameter of the Earth is 12,714,000 metres, you can see 4717 metres, or 4.7 kilometres.

Answer 3

it's not 7 miles, it's about 3 miles. From basic geometry, you get that the distance to the horizon is D=sqrt(2Rh)

where D = distance to horizon R = radius of earth h = height of observer, which would be the height of your eyes.

R and h have to be in consistent units, of course. In feet the radius of the earth is about 4000 mi * 5000 ft/mi or 20 million feet. Standing on the shore, your eyes are maybe 5 feet above the surface, so D=sqrt(2*20e6*5)= 14000 feet, or a little under three miles.

Answer 4

For observers on the ground with eye-level at h = 5 ft 7 in (5.583 ft), the horizon appears at a distance of 2.89 miles.