cloud illusion

Palmpilot said:
Milkman???
Click to expand...
A red meat reference from way back before we all had to choose sides - it featured a character named Milkman Dan.
If it were directed at me I'd take it as a compliment. :D

Fortunately I had saved this for just such an occasion :cool:
milkmandan.jpg

Nauga,
and bug-eyed Earl
 
Palmpilot said:
I suspect that the illusion referenced at the beginning of the thread might be related to the curvature of the Earth. If the top of an undercast has a constant MSL altitude, then the top of the undercast will follow the curvature of the Earth. Consequently, the farthest point you can see on the undercast will be moving away at the same speed as the ground speed of the airplane.
Click to expand...
What made me think of this was not any deep analysis. Some years ago, I was flying to the Phoenix area at night in good VFR conditions, probably at 7500 MSL, and somewhere in the vicinity of Blythe or maybe east of there, I could see a cloud layer ahead, which was illuminated by the Phoenix area city lights. The odd thing was that it looked like the layer was at my altitude, but when I got to the Phoenix area, it was actually much higher. Since weather conditions were stable, I concluded that what I saw must have been due to the curvature of the Earth. (Take THAT, flat Earthers! :D)
 
vibe coded slop. I need to check the math later.
Code: 
$ python3 ./horizon_cloud.py
Aircraft altitude : 7500 ft = 1.4205 mi
Cloud altitude    : 6500 ft = 1.2311 mi
Earth radius R    : 3963.19 sm, refraction k = 1.15

Geometric, no refraction
  Horizon straight line distance : 106.118 sm
  Cloud tangent straight line    : 38.752 sm

Refracted, effective Earth radius Re = k R
  Re = 4557.7 sm
  Horizon distance approx        : 113.798 sm
  Cloud tangent distance approx  : 41.550 sm

Notes:
  * Geometric values are exact for a sphere.
  * Refraction is implemented via the effective Earth radius kR.
  * k = 4/3 is the classic 4/3 Earth used for both maritime and aviation.
    Aviation handbooks often quote k≈1.15-1.33; 1.15 gives the familiar
    1.23 * sqrt(ft) nautical mile rule.
 
I hope you weren't standing in a crosswalk while you did that! :)
 
When I was in college, I used to cover pages with equations. I'm in awe of how smart I used to be.

Usually, there was at least one serious error on the page! :rofl:
 
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