“So, where’s the curvature? If we can’t see it using our own eyes then there’s no curvature, and hence, the Earth is flat!”

That’s a very common position held by most flat-Earthers. So, let’s do some simulation to show that the condition they are demanding is completely unrealistic. We’ll be using the excellent curvature simulation tool by Walter Bislin.

Our eyes have the field of view of about 60°. So, here we’ll use the same value to the simulation, and the result of the simulation will be similar to how our eyes see the curvature.

Keep in mind this means the results of the simulation will not be similar to pictures taken with far different field of view than our eyes. Pictures taken using lenses far wider than 35mm would appear to have more Earth curvature. Conversely, pictures taken using lenses longer than 45mm would appear to have less curvature.

Using the same field of view of 60°, now let’s change the height of the observer in relation to the Earth surface. The higher we are, the more curvature we are able to observe. When we are close the surface of the Earth, the simulation tells us we would not be able to see any curvature, at least not directly. Hence, the fact that we are unable to see curvature while standing on the surface of the Earth cannot be taken as a ‘proof’ that the Earth doesn’t have curvature.

Even when flying at the cruise altitude of a commercial flight, it is still hard to visually discern curvature without any precise measurement. We need to go higher than that.

## References

- Visually Discerning the Curvature of the Earth. By David K. Lynch
- Curvature App: Simulation of Globe-Earth and Flat-Earth – Walter Bislin