Video of New Orleans Superdome Illustrating Curvature and Refraction

Mick West

Administrator
Staff member
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Views of cities across lakes or bays are an excellent way of observing the curvature of the Earth. The distances are easy to calculate, and the building heights are well known. In many cases there are 3D models of the city buildings in Google Earth, so we can recreate the image there to see if it matches what we see.

In an interesting video, David Ray captures images of New Orleans from Fontainebleau State Park in Mandeville, LA. In the video we can see what appears to be the roof of the Superdome

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David gives the camera height as 4 feet (1.22m), so we can recreate this in Google Earth, this is the "expected" view.

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The Superdome (26.5 miles away) is missing! Does this prove the Earth is flat? Of course not, but what's actually going on here?

Well, what if the Earth were flat, and there was no atmosphere, what would the scene look like then? We can get a near perfect approximation in Google Earth by raising the viewpoint 100 meters:
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Well, that does not look like the real-world image either. We can see a lot more of the superdome and the other buildings.

What is interesting here if we take the 100m "expected" view, and overlay it over the "real world" view. First of let's try it by aligning the top of the superdome:
Superdome Aligned - b.jpgSuperdome Aligned - a.jpg


And then by aligning the top of the tallest building:
Superdome Tall building Aligned - b.jpgSuperdome Tall building Aligned - a.jpg


When we use the top of the tallest building as a reference point, the position of the superdome is more where we would expect it, below the horizon. Why? And when we use the top of the Superdome as a reference, why does the top of the tallest building appear a lot lower than it should be?

The answer of course is atmospheric refraction. The thin sliver of the Superdome is just on the horizon, when refraction is at a maximum. The top of the superdome is appearing much higher than it should be, but the top of the tall building is appearing in a more correct position because there is far less refraction when you look up.

"Normal" atmospheric refraction allows you to see further around the earth as the decrease in density of the atmosphere due to pressure bends the light downwards.

This effect is enhanced if there's a temperature inversion, i.e. warmer air on top of colder air. Warmer air is less dense than colder air at the same pressure, so has an even lower refractive index, hence a bigger change as you look up though the atmosphere, so it bends the light more. This phenomenon is called "looming".
 
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Excellent, well considered post. Great use of the juxtoposing/sliding photos to demonstrate your points. I would like to see more people in them Facebook groups link to sources like here, but I unfortunately think that would lead to a lot of "trolls" arriving to these forums.

Great post!!

Bernard.
 

vandamme

New Member
Refraction is well known to radar engineers. They use the "4/3 earth model" to predict height coverage at the horizon. Sometimes big ships can be seen "below the horizon" over hot, humid air like in the Mideast.

To truly show whether the earth is flat with a laser curvature experiment, you'd have to remove all the air. Or at least do it over homogeneous air.

And yes, "below the radar" really is a thing. It wouldn't be, on a Flat Earth.
 
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