# On a clear day, how far away is the horizon?

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• Anonymous

I take that one is standing on a seashore and looking out towards the sea ; then the visible line where the sky meets the water is about 17 to 22 miles.

• Anonymous

2

• It depends on how high up you are.

The horizon is 3 miles away for a 6 foot tall person.

If you're standing on the deck of a ship 20' above the water, it is 6.2 miles.

If you're on the International Space Station 220 miles up, then it is 1339 miles to the horizon.

Please note, this is the distance to the HORIZON, since that is what was asked for. It is not the distance to the farthest object you can see, as this can be considerably farther, since it is possible to see the upper part of objects that are over the horizon. If the other object is as tall as you are, then it is possible to see some of it as much as twice the distance to the horizon. As an example, if you're standing on a 20' high boat, you can see another person standing on another 20' high boat up to 6.2*2=12.4 miles away. Taller objects can be seen even farther.

The formula to calculate the distance between your eyes and the horizon is:

d=sqr(h*h+2rh)

Where h is your height above the ground, and r is the radius of the planet you are on. h and r must be in the same units. sqr() means to take the square root

So if you are 6 feet tall, h=6 feet, and the radius of the Earth is (3963 miles * 5280 feet) = 20924640 feet then the answer is:

d = sqr( 6 * 6 + 2 * 20924640 * 6 )

d = sqr(251095716)

d=15846 feet to the horizon

d=3 miles to the horizon for a 6 foot tall person

If you were orbiting the Earth 220 miles up on the International Space Station, the horizon would be:

d = sqr (220 * 220 + 2 * 3963 * 220 )

d = sqr (1792120)

d = 1339 miles to the horizon for someone on ISS

• Anonymous

Where i live you can see France across the channel if it is a clear day, and see the lights of Calais, Bologne and Dunkirk at night and clearly see the cliffs on the other side, Calais is 22 miles away, but since you can see so much more of the coast, i suppose it must be slightly more

• if your eye-line is relatively at sea point - i.e. you're up on your neck in water - then you relatively're effectual horizon is as distant through fact the actual of the subsequent wave in spite of the shown fact that, i visit assume it quite is not possibly what you meant.. :-) once you're an consumer-friendly person, status on a sea coast which incorporate your ft interior the water - at sea point - on a comfortable day... your eye height would be approximately 5'8" or so... and your reported horizon is around 3 miles.

• If your eye height is about 175 cm from the ground, the earth is supposed to be a complete sphere for simplicity and the earth radius is about 6300 Km approximate, then u can see about 4500 m at the sea level for a flexible surface like the sea.

• According to the military, when I was aboard ship the horizon was 11 miles away, unless mother nature moved it.

Source(s): USCG
• 6 km for a standing man

• Anonymous