Optical illusion in the mountains ― can someone explain?

[Greg Miller]

I figured that may be the case; so I purposely said "seems to be" rather than "is". A range that is level can also appear to be not level if it is not perpendicular to the camera as well - the part of the range that is further away will appear to be lower than the part that is nearer. More perspective stuff..

[jp]

www.heywhatsthat.com is an interesting website that shows an exagerated horizon and the height of all the peaks or landmarks visible from a particular location. One of my customers makes this site. We use it for radio tower purposes. The visibility cloak puts a red mask over what is visible from the location which is quite handy too.

[Leonard Evens]

It is simply perspective (see attachment)

As a mathematician, let me confirm his explanation. The "science" behind this is the fact that what you see and what is recorded on film is the angular displacement of the top of the distant mountan above the line of sight. Ignoring the curvature of the Earth for the moment, you can see that this angular displacement gets smaller as the distance to the mountain increases. That is why, for example, you can entirely block out a high mountain, by putting a few inches of your hand in front of your eye.

[Jehu]

The curvature and refraction should amount to about 186 feet at 18 miles. I've used 4.25 seconds of arc per 1,000 feet as a rule of thumb several times and it's always been pretty close.

Signed: a Land Surveyor

[jb7]

As a mathematician, let me confirm his explanation. The "science" behind this is the fact that what you see and what is recorded on film is the angular displacement of the top of the distant mountan above the line of sight. Ignoring the curvature of the Earth for the moment, you can see that this angular displacement gets smaller as the distance to the mountain increases. That is why, for example, you can entirely block out a high mountain, by putting a few inches of your hand in front of your eye.

Or...

http://www.youtube.com/watch?v=8vbd3...e_gdata_player

[Heroique]

Mount Olympus is about 17-18 miles away.

The curvature and refraction should amount to about 186 feet at 18 miles. I've used 4.25 seconds of arc per 1,000 feet as a rule of thumb several times and it's always been pretty close. Signed: a Land Surveyor.

Nice.

Not just the “186 feet.”

But the pure calm of mathematics.