If I was standing on a flat plain that stretched for 100s of miles?

Question

and I looked at the sky at the horizon. With no variance whatsoever in altitude, how far away would that horizon be?

Answer 1

Well, if it was truly a flat plane, you would see to wherever the plane ends (if it does). If you mean you are standing on the Earth where the terrain is smooth (but curved), then the distance depends on how tall you are. The horizon would be where your line of sight is tangent with the spherical surface of the Earth. The Earth isn't a perfect sphere but say it is for now. To get the distance to the horizon (d) just do this calculation:

D = (R+h)^2 - R^2

where:

R = the Earth's radius (6,378,135 meters) and
h = your height in meters

Now take the square root of D to get d.

Say you are 5 ft or about 1.5 meters tall. Then d is about 4374 meters or about 2.7 miles

This is only approximate though. There are a lot of other factors you'd need to be exact.

Answer 2

at 10' above the ground the horizon is 26 miles away

Answer 3

Infinity
If you were standing on an absolute flat plain you would not be on earth or any other planet. If the planeextended to infinity the horizon would also.

Answer 4

none of these people know what they are talking about. the earth is a sphere! a sphere is not flat. You would see the horizon 100's of miles away!

Answer 5

about 3 miles

Answer 6

In other words, if you were standing on a perfectly-smooth earth, or looking out over the ocean? Roughly 3 miles.

Answer 7

12 miles

Answer 8

approx. 6 miles

Answer 9

i'm with the navy man. 26 miles.

Answer 10

I would guess that it would be at the end of the plain.