Distance to the Horizon
I very often fly with a passenger in the right hand seat. Without fail, they always ask - "How far can I see from up here?".
I am forced to answer that I don't know exactly (or even inexactly), so my question is, does anybody out there know a rule of thumb for working out the (theoretical) distance to the Earth's horizon given your height in 1000's of feet?
Many Thanks in advance...