On an "extreme clear" (pilot lingo) day, how far is it from the point where you stand to the horizon?

Question

I saw a reference to this in a weather program, but no indication was made as to how far each of us is from the horizon that we observe. Any info would be appreciated.

Answer 1

A good approximation can be had with the following expression;

d = √ (2Rh)

where d is the visible distance to the horizon, 2R is the diameter of the Earth, and h is the height of the observer. So, for example, using the English system, assuming the observer is 6 feet high, we have:

x = √ ( (8000 miles) (6 feet) / (5280 feet per mile) ) = 3 miles, approximately. If you stand on the shore of the ocean with waves lapping at your feet, that's about how far the horizon is, before the ocean curves down beyond.

If you were on a cliff overlooking the ocean, say, 100 feet up, then we have:
x = √ ( (8000 miles) (100 feet) / (5280 feet per mile) ) = 12.3 miles, before it starts curving down beyond.

On a clear day, people in fact can see much farther than that, but they usually fail to notice that objects seen further away than the horizon are actually slightly behind the horizon. This is how ancient Greek seafarers became aware that the Earth is round, they could see the tops of distant ships peeking over the horizon.

The expression d = √ (2Rh) is the first term of the series expansion for the equation of the circle of the Earth, so it works well for small h relative to 2R.

Answer 2

That would depend. Are you standing on a flat surface at sea level? Are you standing on a mountain top at 2 miles above sea level. the distance you can see or view is related to the height above sea level tha tyour standing at. So at sea level in is only about 3 to 5 miles and from 2 miles up it can be as far as 30 to 50 miles or more.

do some research on line re: distance to horizon

Answer 3

As far as the eye can see maybe??

Answer 4

CAVU CLEAR AND VISIBILTY UNLIMITED. I THINK IS WHAT YOU ARE LOOKING FOR.