Writer's Reference: Distance to the Horizon

[You've entered the Giveaway in Support of YA Asian Book Covers, right? Today might be your last chance! (Boy, I should've thought of a better name).]



How far is it to the horizon? How far away can you see an approaching object? This is something I come across in Air Pirates a lot, but it always takes multiple clicks and conversions to get at the simple formula I want. So, fully expecting mathematics to drive away half my audience, here it is (in both kilometers and miles):





So someone 5 ...