The horizon appears flat because the curvature is too small when observed from near the Earth’s surface. However, in some cases, we can exaggerate the curve by taking photographs of the horizon and then magnifying the results vertically.
Magnifying in such a way will also magnify the distortions introduced by the camera lens. We will need to control these distortions using proper photography techniques, or by placing a known straight object as a control object in the frame, close to the horizon. If successful, then the remaining curvature in the photograph can only come from the curvature of the Earth.
The required conditions:
- Use a wide-angle lens. The wider the lens is, the better.
- Take the picture from a high enough location. The higher the location is, the better.
- The horizon line is visibly sharp with enough contrast, not blurred.
The wider the lens and the higher the observer’s position, then the larger the curvature will appear, and the less possibility to be affected by lens distortions. To control the distortion, we can do these things:
- Using a high-quality camera and a wide-angle lens.
- Placing the horizon line at the center of the frame.
- Turning on the distortion correction in-camera, or fix the distortions in post-processing.
- Placing a known straight object near the horizon line as a control.
To do the same for third party pictures on the Internet, these are various tips to get suitable images:
- Find images taken from a high position using a wide-angle lens.
- Find photos with a high resolution.
- A wide-angle lens usually has barrel distortion. Because we cannot know whether the photographer bothered to correct the distortion, it is a good idea to find pictures where the horizon line is right in the middle, where the distortion is minimal.
- We can also find pictures where the horizon line is below the center point. If the photo has barrel distortions, then a horizontal straight line below the center point will appear concave. If the result is convex, then there’s a good possibility that the curve of the horizon overwhelms the effect of barrel distortion.
- Many photographs retain an EXIF metadata where we can examine to know how the picture was taken, including the brand of camera & lens, and the focal length.
Even though it cannot be 100% reliable, by picking pictures using the above criteria, we can maximize our chance of getting a suitable picture with minimal distortions.
To magnify the images vertically, we can use image processing software like Photoshop or GIMP; or graphic design software like Adobe Illustrator or Inkscape.
The Reasons We are Showcasing the Images in the Illustration
These are our reasons why we are using these images in the illustration.
Picture 1 (by Clouds Givemethewillies): Using a known straight object as a reference, placed very close to the horizon. Even if the yellow straightedge appears slightly curved after magnified vertically, the horizon curvature is far more pronounced. The picture was taken high enough above sea level. This is the first picture to showcase the vertical magnification technique.
Picture 2 (by JTolan Media1): A flat-Earther took the picture. The horizon is placed in the middle of the frame, where the distortion is minimal. The photo was taken from a flight and will give us a pronounced curvature.
Picture 3 (by us): We took this picture ourselves using a pro camera Canon EOS R that has a high resolution, and using a pro-grade lens Canon EF 16-35 f/4L IS USM, which has low distortion. We turned on distortion correction in-camera. Used a straight glass railing as a reference object, and it remains straight after magnification. Both the horizon line and the glass railing were placed in the middle of the frame that has minimal distortion. The resulting curvature matches the simulated result.
Picture 4 (by Rory): Picture was taken from a high enough cliff next to the ocean. It used a known straight object as a reference. The horizon is placed in the center of the frame that has minimal distortion. The resulting curvature matches the simulated result.
Picture 5 (by Rob Skiba). A flat-Earther took the picture. Taken from a high-altitude balloon using a modified GoPro with a non-fisheye lens. The horizon line was placed in the middle of the photograph that has minimal distortion.
Picture 6 (by Wolfie6020): The photo was taken from cruising altitude of an airline. The curvature is already visible even before magnification. The horizon was placed at the center of the image that has minimal distortion.
The following pictures were taken by third parties unrelated to flat-Earth related arguments. These pictures are not as strong evidence as to the above images, but with various considerations, they are still useful as evidence for Earth’s curvature and are good examples of how to find suitable images for the purpose explained in this article.
Picture 7 (by Pixabay): The horizon line is below the centerline, which —if the barrel distortion exists— will make a straight line concave. After magnification, it appears convex, and we can conclude there is a high possibility that the horizon line curves more than the barrel distortion curved the image. The image was also taken from a high enough position next to the ocean.
Picture 8 (Nobody Hikes in LA): The horizon line is placed in the middle of the frame that has minimal distortion. The photo was taken from a high enough altitude. The resulting curvature matches the simulated image from Google Earth.
Picture 9 (Lenny K Photography): The horizon line is placed below the center point. If the distortion was not controlled, it would cause a straight line to appear concave. The magnified horizon is convex, and therefore there is a good possibility that the horizon curvature at least overwhelms the distortion introduced by the lens if any. The picture was taken from cruising altitude of an airline. From its EXIF metadata, we know that it was taken using a pro-grade Nikon D800 with a fixed lens 35mm f/1.4 that has indiscernible distortion.
Picture 10 (Ocean Reef Resorts): The horizon line is placed in the middle of the frame, which has minimal distortion. It includes an EXIF metadata, informing that the picture was taken using the Canon EOS 50D using Canon EF-S 10-22 mm f/3.5-4.5 USM. The situation is very similar to picture #3 above.