Indeed, I did see that, and it's just really hard to make any sense out of it. Like there's a haze out there that's sky colored, right? Once you get too far from the viewer, everything just turns to the sky color... I guess? Except the Sun and the moon... and the stars... and stuff.
So yeah that makes no sense whatsoever... but there you go. /shrug
Ok, if view limitation by air makes no sense, let's elliminate it from the equation.
This diagram here shows two observation points: altitude of U is 10 km, altitude of L is 1 km.
In reality:
- U will have horizon at A, 357.3 km away
- L will have horizon at B, 112.9 km away
In Flat model:
Looking from L, the segment of the ground that covers 1/60th of a degree (1 arc minute) is from A to C.
C is at
323.66 km, which is
33.64 km closer than A.
If we select some random point M at, say, 233 km, then the ground segment between A and M will seen from L have angular size of 0.086 degrees (5.16 arc minutes).
That is more than 5 times bigger than the average human ability to distinguish details.
Why L can't see the segment AC?
Why L can't see the segment AM?
Why L can't see beyond B?SL = 1 km
SU = 10 km
SB = 112.9 km
SM = 233.0 km
SC =
323.66 km
SA = 357.3 km
ALC = 1 arc min (1/60 = 0.0166666 degrees)
ALM = 5.16 arc min (0.086 degrees)
ALB = 21 arc min (0.35 degrees)
EDIT: I've made a mistake calculating C. The correction is in bold.