# Earth curvature refraction experiments - debunking flat/concave Earth

Sorry, I am not as advanced in technology (or etc?) as you are. What's that that you are talking about if you don't mind to share with me? GoPros? Once in the past I was confronted by a flat-earther (which I found debilitating) and I had no argument to confront them with on why the Earth was round. From then on I would like to arm myself, with a help of this forum, I hope?

GoPros are small tough cameras often used on balloon ascents.

There are two type of camera lenses: curvilinear and rectilinear. Curvilinear lenses make straight lines look curved.

GoPros have curvilinear lenses, so they make the horizon look curved unless it goes through the exact center of the image. See this video after 7 minutes for examples of the horizon curving in both directions.

And two seconds later:

What's that that you are talking about if you don't mind to share with me? GoPros?
GoPros are little durable "action cameras" that you may have noticed cyclists wearing on their helmets. I'm no expert but it seems most amateur/civilian high altitude footage uses them because they give a nice wide field of view due to the fisheye lenses. The downside of this - as far as the flat earth argument is concerned - is that any curvature of the earth (or lack of) is not an accurate representation of what is actually there, because of the way the fisheye 'distorts' the images.

Fifteen seconds of this video demonstrates that quite well:

So while it may at first seem that we're looking at the curvature of the earth, as the horizon moves into the centre of the frame, it straightens, and then becomes concave, all due to the lens.

Flat earthers like to use this by (erroneously) asking, "Why is every single video that supposedly shows the curvature of the earth shot with a GoPro?"

That's how I understand it anyway. I'm sure someone else can explain it better.

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I'm sure someone else can explain it better.
Told ya. I didn't even have chance to finish my post before Mick got in there.

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Very interesting indeed. Thanks for explaining it in detail. Flat-earthers would say "it hit the firmament" when the helium balloon bursts. Do you know of any camera, experiment, a video that shows a true a curvature of the Earth to use as an educational tool? Also, does anyone know how much this kind of helium balloon experiment cost?

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P.S.: At 33 km altitude horizon is how far? ~650 km? And the horizon seems flat? Perhaps 650 km is not far/wide enough in order to see curvature. I really would like to get something on my hands to show my FE friend and his kids that Earth is a sphere and not a stupid dripping pancake or a never ending plain. I hope you guys can lead me to a video etc. that explains it without complex formulas as a no brainer. Thanks a lot.

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Research suggests you need to get to around 60,000 feet to be able to clearly discern the curveture of the earth, and at the very least 35,000 to have any chance of detecting it.
http://thulescientific.com/Lynch Curvature 2008.pdf
Reports and photographs claiming that visual observers can detect the curvature of the Earth from high mountains or high-flying commercial aircraft are investigated. Visual daytime observations show that the minimum altitude at which curvature of the horizon can be detected is at or slightly below 35; 000 ft, providing that the field of view is wide (60°) and nearly cloud free. The high-elevation horizon is almost as sharp as the sea-level horizon, but its contrast is less than 10% that of the sea-level horizon. Photographs purporting to show the curvature of the Earth are always suspect because virtually all camera lenses project an image that suffers from barrel distortion. To accurately assess curvature from a photograph, the horizon must be placed precisely in the center of the image, i.e., on the optical axis.
...
Interviews with pilots and high-elevation travelers revealed that few if any could detect curvature below about 50; 000 ft. High-altitude physicist and experienced sky observer David Gutierrez [6] reported that as his B-57 ascends, the curvature of the horizon does not become readily sensible until about 50; 000 ft and that at 60; 000 ft the curvature is obvious. Having talked to many other high fliers (SR-71, U2, etc.), Gutierrez confirms that his sense of the curvature is the same as theirs. Passengers on the Concorde (60; 000 ft) routinely marveled at the curvature of the Earth. Gutierrez believes that if the field of view (FOV) is wide enough, it might be possible to detect curvature from lower altitudes. The author has also talked to many commercial pilots, and they report that from elevations around 35; 000 ft, they cannot see the curvature
Content from External Source

ISS is at ~400km and one can see just a slight curvature, so I can imagine what can be detected at 35000 ft. to 60000 ft. which is 10 to 20 km in altitude. The above video had camera at 109000 ft. which is about 35km in altitude, which is over 20 miles and still the center of the lens showed no curvature. Which says to me that one has to be at least 200-400 km to detect any curvature. This is why flat-earthers can not see any (at ground level or at 100K ft.) and are clapping their hands with joy. Yet they have no idea how to take photos of the "underside" or "the edge" of the FE

By the way, why does NASA not take photos of Earth much from the Moon or from Mars orbiter mission? Or do they? Send a satellite 6000 to 10000 miles away from Earth and take all kinds of photos. That's where from you can see the entire spherical Earth, I believe. Why not place an observer camera on the surface of the Moon and have it live on the internet, or at least recorded video or photos.

Research suggests you need to get to around 60,000 feet to be able to clearly discern the curveture of the earth, and at the very least 35,000 to have any chance of detecting it.
http://thulescientific.com/Lynch Curvature 2008.pdf
Reports and photographs claiming that visual observers can detect the curvature of the Earth from high mountains or high-flying commercial aircraft are investigated. Visual daytime observations show that the minimum altitude at which curvature of the horizon can be detected is at or slightly below 35; 000 ft, providing that the field of view is wide (60°) and nearly cloud free. The high-elevation horizon is almost as sharp as the sea-level horizon, but its contrast is less than 10% that of the sea-level horizon. Photographs purporting to show the curvature of the Earth are always suspect because virtually all camera lenses project an image that suffers from barrel distortion. To accurately assess curvature from a photograph, the horizon must be placed precisely in the center of the image, i.e., on the optical axis.
...
Interviews with pilots and high-elevation travelers revealed that few if any could detect curvature below about 50; 000 ft. High-altitude physicist and experienced sky observer David Gutierrez [6] reported that as his B-57 ascends, the curvature of the horizon does not become readily sensible until about 50; 000 ft and that at 60; 000 ft the curvature is obvious. Having talked to many other high fliers (SR-71, U2, etc.), Gutierrez confirms that his sense of the curvature is the same as theirs. Passengers on the Concorde (60; 000 ft) routinely marveled at the curvature of the Earth. Gutierrez believes that if the field of view (FOV) is wide enough, it might be possible to detect curvature from lower altitudes. The author has also talked to many commercial pilots, and they report that from elevations around 35; 000 ft, they cannot see the curvature
Content from External Source

I must say that I backed away from these two arguments often put to flat earthers online, seeing the curvature from aircraft and the high altitude videos. As you say, it seems from published research that only Concorde passengers ever got high enough to see any curve, and given the narrow angle of view from the Concorde's little porthole windows, I'd feel a bit unhappy denying the possibility of wishful thinking. Flight crew in the cockpit would have a wider view, but I expect they would be claimed to be members of the elite, in on the conspiracy.

And I looked at a number of amateur high altitude camera videos, and like #Rory I saw a lot of barrel distortion bending the horizon both ways, s well as flattening it, within a period of a few seconds. I couldn't find anything amateur that was compelling.

By the way, why does NASA not take photos of Earth much from the Moon or from Mars orbiter mission? Or do they? Send a satellite 6000 to 10000 miles away from Earth and take all kinds of photos. That's where from you can see the entire spherical Earth, I believe. Why not place an observer camera on the surface of the Moon and have it live on the internet, or at least recorded video or photos.

They (and other space agencies) do. There's lots of photos on a daily basis from satellites in high orbits that show the full disk of the earth. For example the Japanese Himawari-8 satellite:
http://rammb.cira.colostate.edu/ramsdis/online/himawari-8.asp

Check out the last four week's images:
http://rammb.cira.colostate.edu/ram...l_disk_ahi_natural_color&width=800&height=800

Heres's a segment of the high-res version of that image:

I don't think one can fake those, although flat-earthers may pick up the words "full disk" Actually I found one as well, with a very interesting description of the job:

"On February 11, 2015, DSCOVR was finally lofted into space by a SpaceX Falcon 9 rocket. After journey of about 1.6 million kilometers (1 million miles) to the L1 Lagrange Point, the satellite and its Earth Polychromatic Imaging Camera (EPIC) has returned its first view of the entire sunlit side of Earth. At L1—four times farther than the orbit of the Moon—the gravitational pull of the Sun and Earth cancel out, providing a stable orbit and a continuous view of Earth."

http://earthobservatory.nasa.gov/IOTD/view.php?id=86257&eocn=image&eoci=related_image

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Yep. And we can also look at both DSCVR and Himawari-8 images from approximately the same time and see the same cloud patterns - and see things like hurricane formations that were predicted and experienced on the ground. That's pretty neat.
As you say, it seems from published research that only Concorde passengers ever got high enough to see any curve, and given the narrow angle of view from the Concorde's little porthole windows, I'd feel a bit unhappy denying the possibility of wishful thinking.
Flat earthers also counter this by saying the windows themselves are curved at the edges, and that's what produces the appearance of a curve, if there is one. I haven't been in a plane since I got into this but I'm flying next week so looking out the window will probably be more interesting than usual.
ISS is at ~400km and one can see just a slight curvature.
I'd say it's plenty more than slight:

Flat earthers also counter this by saying the windows themselves are curved at the edges, and that's what produces the appearance of a curve, if there is one. I haven't been in a plane since I got into this but I'm flying next week so looking out the window will probably be more interesting than usual.

I've flown in an airliner since I read that claim. The first thing I noticed was that none of the airport buildings, light poles, built up areas on the ground or anything rectilinear looked in the slightest bit curved or circular through the windows! Seems only the horizon would be subject to this effect, according to flat earthers. As I said, I don't belive we could see a curvature below 60,000 ft,, based on researchI've read, but this FE claim makes no sense in its own terms.

I've flown in an airliner since I read that claim. The first thing I noticed was that none of the airport buildings, light poles, built up areas on the ground or anything rectilinear looked in the slightest bit curved or circular through the windows!
Good point. And then there's the other aspect that the windows don't generally allow a wide enough angle of view.

All water settles with a flat surface, its the nature of water. It conforms to whatever vessel you put it in. You could create a curved vessel with an open top and the water will always have a flat surface. You can not use this to measure the type of vessel the water is in. This is a misunderstanding of the laws of nature , gravity and the nature of water its self. Water is not the surface or structure of the planet. Its illogical to use it to measure what the surface or over all structure of the vessel it is in. Would one say the actual surface of the earth at the bottom of the ocean was flat and smooth because the surface of the water is? So naturally the curve of the earth is going to be much more gradual over the surface of water. Maybe almost undetectable. depending on distance. I think 20 miles is very minuscule in comparison to the actual distance across the Pacific or Atlantic. Mankind is losing its perspective on its own physical size in relation to the size of the globe they are on. Most likely psychological due to technology and advanced communications which has mentally made the world much smaller....but not physically.

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Would one say the actual surface of the earth at the bottom of the ocean was flat and smooth because the surface of the water is?
No, but on a large scale you can say it has a curve, because the water surface is curve. The flatter water just lets you observe and measure this curve more accurately.

No, but on a large scale you can say it has a curve, because the water surface is curve. The flatter water just lets you observe and measure this curve more accurately.
Exactly

No, but on a large scale you can say it has a curve, because the water surface is curve. The flatter water just lets you observe and measure this curve more accurately.
I guess what I am also saying is that the only FE experiments I have seen are ones trying to measure the surface of the earth by measuring the surface of large bodies of water. They dont account for any of the outside variables of nature and the fact that water has completely different properties than a solid does. They are using formulas as if they were in a controlled sterile lab or vacuum. Also acting as if the surface of the planet it self is that of a smooth solid bowling ball type of nature. Dismissing or ignoring the effect gravity has on water which causes it to be consistently flatter on its surface than natural earth (dirt, Mountains etc...) that water is NOT the surface of the planet but is a liquid that exists on The surface. So logically you would have to measure a much greater distance than 20 miles to detect the curvature of the earth if using controlled vacuum formulas. Also the natural state water forms are drops or small spheres when not impeded by an outside force such as gravity or air or a vessel. The high and low tides themselves should also be a factor in measuring this curvature using a large body of water such as the oceans.

I guess what I am also saying is that the only FE experiments I have seen are ones trying to measure the surface of the earth by measuring the surface of large bodies of water. They dont account for any of the outside variables of nature and the fact that water has completely different properties than a solid does. They are using formulas as if they were in a controlled sterile lab or vacuum. Also acting as if the surface of the planet it self is that of a smooth solid bowling ball type of nature. Dismissing or ignoring the effect gravity has on water which causes it to be consistently flatter on its surface than natural earth (dirt, Mountains etc...) that water is NOT the surface of the planet but is a liquid that exists on The surface. So logically you would have to measure a much greater distance than 20 miles to detect the curvature of the earth if using controlled vacuum formulas. Also the natural state water forms are drops or small spheres when not impeded by an outside force such as gravity or air or a vessel. The high and low tides themselves should also be a factor in measuring this curvature using a large body of water such as the oceans.

Not true. For any body of water larger than a few feet the upper surface of the water is the most accurate representation of the overall curve of the planet you can get. It just LOOKS flat, but it's actually curved. I've observed this curve in as little as three miles, see here:
https://www.metabunk.org/folsom-lake-photographs-demonstrating-the-curvature-of-the-earth.t7789/

The water level will drop 8 inches over the first mile. You can measure this.

And there are unconfirmed reports of it being observed in as little as 800 feet, with the reflecting pool at the Christian Science Plaza in Boston.

Not true. For any body of water larger than a few feet the upper surface of the water is the most accurate representation of the overall curve of the planet you can get. It just LOOKS flat, but it's actually curved. I've observed this curve in as little as three miles, see here:
https://www.metabunk.org/folsom-lake-photographs-demonstrating-the-curvature-of-the-earth.t7789/

The water level will drop 8 inches over the first mile. You can measure this.

And there are unconfirmed reports of it being observed in as little as 800 feet, with the reflecting pool at the Christian Science Plaza in Boston.

I rather liked this video looking across to the island of Ailsa Craig. It shows in an unbroken take how moving a short distance down to the water's edge causes previously visible building on near sea level on the island to disappear below the curvature.

To make this clearer I made a "blink comparison" animation that flicks between the higher and lower viewpoint

And put in the stills for good measure

I realise that hardcore flat earth believers will just mutter about an imaginary "law of perspective" unknown to optical science or art. Or "photoshop! "CGI!" Not much we can do about that.

Wow thats great! thanks for the info. I have been looking into this FE theory for over 3 months now. All their footage contradicts what you are saying. They say they have laser tested the surface of the water and there is no differential drop in 20 miles. Sometimes longer distances. Videos using the ocean and across the English Channel. The only way that would be possible is what I have already explained. When one YouTubes the subject there are hardly any videos debunking FE with actual footage or experiments, but tons of videos supporting FE. Thanks again.....P.S. the water pool at the christian science church in Boston was part of my old stomping grounds lol.

To make this clearer I made a "blink comparison" animation that flicks between the higher and lower viewpoint

It also looks as though the more distant land (visible at the right hand edge, behind the island), "drops" by a larger amount than the island itself as the viewpoint gets lower. Intuitively it seems that more distant objects should appear to move less with a shifting viewpoint (as seen from a moving car, for instance), but thinking about it, if you take into account the curvature, then moving to a lower viewpoint should raise nearer objects relative to further ones. So in fact it is the island (and the sea level horizon) appearing to "rise" relative to the more distant landmass.

It's complicated a bit by the fact that the shoreline appears to change shape between the two viewpoints, too.

Do you know the distance that is? from the shore line to the island?

Not true. For any body of water larger than a few feet the upper surface of the water is the most accurate representation of the overall curve of the planet you can get. It just LOOKS flat, but it's actually curved. I've observed this curve in as little as three miles, see here:
https://www.metabunk.org/folsom-lake-photographs-demonstrating-the-curvature-of-the-earth.t7789/

The water level will drop 8 inches over the first mile. You can measure this.

And there are unconfirmed reports of it being observed in as little as 800 feet, with the reflecting pool at the Christian Science Plaza in Boston.

I do wonder about the reflecting pool though. How would one decipher between the curvature of the earth and merely the foundation of the pool or a slight bulge in the earth it was built on?

I do wonder about the reflecting pool though. How would one decipher between the curvature of the earth and merely the foundation of the pool or a slight bulge in the earth it was built on?

Quote you: "All water settles with a flat surface, its the nature of water".

Quote you: "All water settles with a flat surface, its the nature of water".[/QUOut
Right! must be too early lol

Do you know the distance that is? from the shore line to the island?

8.8 Miles
Beach is at 55.171606°, -4.933531°

I do wonder about the reflecting pool though. How would one decipher between the curvature of the earth and merely the foundation of the pool or a slight bulge in the earth it was built on?
The bottom of the pool is entirely irrelevant to the curve of the surface. It could be two miles deep, with a 1.99 mile high monolith in the middle, and the top would still follow the geoid of the Earth.

Wow thats great! thanks for the info. I have been looking into this FE theory for over 3 months now. All their footage contradicts what you are saying. They say they have laser tested the surface of the water and there is no differential drop in 20 miles. Sometimes longer distances. Videos using the ocean and across the English Channel. The only way that would be possible is what I have already explained. When one YouTubes the subject there are hardly any videos debunking FE with actual footage or experiments, but tons of videos supporting FE. Thanks again.....P.S. the water pool at the christian science church in Boston was part of my old stomping grounds lol.
You are welcome. I put a couple more videos on the same page, which you can find here.
http://roundearthsense.blogspot.co.uk/2016/03/138-another-favoriteproof-of-ball.html

and there's a lot of good stuff in the FE section here, as I expect yoy'be seen already.

It also looks as though the more distant land (visible at the right hand edge, behind the island), "drops" by a larger amount than the island itself as the viewpoint gets lower. Intuitively it seems that more distant objects should appear to move less with a shifting viewpoint (as seen from a moving car, for instance), but thinking about it, if you take into account the curvature, then moving to a lower viewpoint should raise nearer objects relative to further ones. So in fact it is the island (and the sea level horizon) appearing to "rise" relative to the more distant landmass.

It's complicated a bit by the fact that the shoreline appears to change shape between the two viewpoints, too.
If you watch the video, I think the path down to the water's edge took the camera person a little to his left, as well as down.

Do you know the distance that is? from the shore line to the island?
The video is taken from the monument in Lendalfoot. Google Maps location here.

That's a little under 9 miles from the closest point of Ailsa Craig:

The coast of Kintyre, visible immediately to the right of Ailsa Craig, is over 30 miles distant:

As for the movement to the left, I am not sure that would be large enough to have much of an effect at this distance.

I do wonder about the reflecting pool though. How would one decipher between the curvature of the earth and merely the foundation of the pool or a slight bulge in the earth it was built on?
The bottom of the pool is entirely irrelevant to the curve of the surface. It could be two miles deep, with a 1.99 mile high monolith in the middle, and the top would still follow the geoid of the Earth.
Excellent, thanks Mick. I may have to add that to the page.

If you watch the video, I think the path down to the water's edge took the camera person a little to his left, as well as down.

The distance is only a few metres horizontally:

First viewpoint:

Second viewpoint:

That is the same rock visible in both, and the vantage point is shifted by less than the length of the rock. No more than about 10 metres, which would not produce much parallax error over that distance at all.

Can one accurately measure a 0.5° angle with it, I wonder?
I've been playing with it the last few days and, though it claims an accuracy of 0.1°, I'm not sure I'd trust it even to 0.5° - it sometimes returns results significantly different, even of the same shot. Plus, because the on-screen elevation is usually a long way out, and calibration is done by the user, I don't think any particular picture could be used to discern anything.

Link to my tinkerings with it here.

I've flown in an airliner since I read that claim (that airplane windows create a fake curve of the earth). The first thing I noticed was that none of the airport buildings, light poles, built up areas on the ground or anything rectilinear looked in the slightest bit curved!
Yep, seems like it's just at the very edge of the window where any curve is produced:

Yep. And we can also look at both DSCVR and Himawari-8 images from approximately the same time and see the same cloud patterns - and see things like hurricane formations that were predicted and experienced on the ground. That's pretty neat.
This is the image from DSCVR taken on August 1st at 02.24GMT:

And this is Himawari-8, at 02.30 on the same day:

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I've improved the curvature calculator a bit, tidying up, and added "drop" calculations
https://www.metabunk.org/curve/

Wth easier cut and paste:

For distance = 4 Miles (21120 Feet) and Viewer Height = 6 Feet (72 Inches)
Horizon = 3 Miles (15838 Feet)
Bulge = 2.67 Feet (32.01 Inches)
Drop = 10.67 Feet (128.03 Inches)
Hidden= 0.67 Feet (8.01 Inches)
Content from External Source

I'll continue to tidy it up.

For fans of south Wales here are some photos of it disappearing. One is from my garden and the other from higher up. Looking towards Cardigan and Stumble head from Aberystwyth. I cannot see the Strumble lighthouse light from home, but can see the beam on the clouds under good conditions. Hewers amongst you may spot a shoal of mackerel.

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I realize this is not of interest to many people, but I like to get things right. Anyway, here's another way of rendering the surface of the lake more accurately:

A squiggly path across the lake:

And verify it works fine at sea level:

Actually a few pixels off, but way better than the lake obscuration
I live in Wellington, New Zealand and Owhiro Bay is not far from where I live. I could take some photos and also have a Wild Heerbrugg T2 theodolite and could measure some angles if that would help.

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Hello all, I am not a flat earth believer (although they pose some very valid points). I have some questions regarding the video of Ailsa Craig, below are two pictures I grabbed from an above post. Forgive the sloppiness of it all, but I believe it will suffice. Each arrow I made over the image showing the building, then copied it onto the next image where it is missing.

-The height of the island remains somewhat the same, even though it appears that in loosing the building we should see a drop in height.

-The two arrows on each side are off marks that are recognisable in each image, although it seems that we do loose some height, in comparison to the building it (or some of it) should still be visible.

-The image of the building is mirrored on the water, I assume, yet it is clearly above the horizon line. How does that happen?

-Looking left of the vertical arrow showing height there are some clear whitish rocks which are visible on second photo yet the relation in which they disappear does not correspond with the building.

Thanks

Basically refraction. The image is bending and stretching over the horizon, and exactly what bends varies with the view altitude.

The "reflection" of the buildings is an inferior mirage. The stretching is called towering.

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