Two friends of mine are having a friendly dispute about a bit of math. The crux of the problem is this: If the earth were perfectly spherical, how much "bend" would there be in 260 miles? Or, in other words, how tall would a mountain 260 miles away have to be for its top to be visible?

The math for this is beyond me (maybe 40 years ago I knew how to figure it) so please try to keep the explanation relatively simple.

tanstaafl.