Observing Earth’s Curvature From a Flight

At the cruising altitude of a jet airliner, Earth’s curvature is too slight for us to notice casually. But with planning and careful observation, it is not impossible to see the curvature.

Observing the curvature on a flight is easier by taking a photo of the horizon and carefully examining the results. An ultra-wide rectilinear lens has a broader field of view than a human eye. Therefore, more curvature will be visible.

Make sure to get a window seat!

Before taking off, take photos of various objects known to be straight to ensure that straight lines remain visibly straight in the photos. No lens is perfect, and all of them will have some distortions. To minimize distortions, place the straight lines in the center of the frame where the distortion will be minimal. Many cameras can also fix distortion digitally, and we need to make sure it is enabled. Some post-processing software can also correct distortions, especially if the images are in the RAW format.

The biggest challenge is that the horizon will appear blurred most of the time and it is hard to distinguish the surface from the sky. To alleviate the problem, we can do one of these:

  1. Increase the contrast of the image of a blurred horizon. This can be easy or difficult depending on the resulting image.
  2. Use an infrared or night vision camera. It can penetrate the haze and reveal the clearly defined horizon.
  3. Find the right time where the horizon appears sharp, like after sunset, or before sunrise.

To make it easier to recognize the curvature, we can magnify the resulting photos vertically during the post-processing.