Hello. 2 questions, one of which I think is a math problem and the other of which is technical and has to do with airplanes.
I am standing somewhere on the earth where the terrain is perfectly level for literally as far as the eye can see. I have some kind of binoculars or other optical device that allows me to see basically forever. How far away will my 6-foot tall friend have to be before I cannot see him due to the curve of the earth?
What do pilots mean when they talk about “10 miles” visibility, etc (i.e. at such times it often seems like you can see a lot further than 10 miles).