Q:

How far away is the horizon?

A:

Quick Answer

The distance to the horizon depends on the height of the observer. For a 6-foot-tall individual standing at sea level, the horizon is about 3 miles away. Viewed from a height of 8 inches, the horizon is about 1 mile away.

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How far away is the horizon?
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Full Answer

The distance to the horizon is the farthest point the eye can see before the earth curves out of view. That distance changes relative to the height of the observer. Given an unobscured view from 60 feet above sea level, the horizon is about 9 miles away. From 200 feet above sea level, it is almost 17 miles away. From the top of Mt. Everest, at more than 29,000 feet above sea level, the horizon is over 200 miles away.

Because the line of vision is a straight line running tangentially to the curve of the earth, a right triangle is formed with one vertex at the point of observation, another at the apparent horizon and the third at the center of the earth. The distance from observer to horizon can be found by using the Pythagorean theorem, which states that the squares of the two shorter sides of the triangle added together are equal to the square of the longest side. The distance derived from the calculation must be regarded as an approximation because the earth's atmosphere refracts light, resulting in distortion. In standard atmospheric conditions, the actual distance to the horizon is about 8 percent greater than the calculated distance.

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