**A Tabletop Experiment for Flat Earth Supporters**
Distances between cities have been measured for many centuries. This is the domain of geodesy—the science of the Earth's shape and size. Between cities there are roads of known length, railway routes, air connections, satellite navigation, detailed maps, and results of geodetic measurements.
So let’s take a simple starting point: the distances between major cities are known with sufficient accuracy. If you believe these data cannot be trusted, then arguing about the shape of the Earth is pointless—in that case, you would first need to personally re-measure the distances between cities using triangulation and a theodolite, and only then continue reading.
Now, the experiment itself.
Take four cities forming a large quadrilateral. For example:
* Moscow
* Kazan
* Saratov
* Voronezh
Find the distances between every pair of cities:
* Moscow – Kazan: ~720 km
* Moscow – Saratov: ~720 km
* Moscow – Voronezh: ~470 km
* Kazan – Saratov: ~520 km
* Kazan – Voronezh: ~810 km
* Saratov – Voronezh: ~510 km
In total, you get six distances—four sides and two diagonals.
Now build a model:
at a scale of 1 cm = 100 km, cut out six strips:
* 7.2 cm
* 7.2 cm
* 4.7 cm
* 5.2 cm
* 8.1 cm
* 5.1 cm
And now comes the interesting part.
Try to assemble these six strips on a perfectly flat table into a single figure that satisfies all distances simultaneously—a quadrilateral with both diagonals. Not three distances, not four, but all six at once.
If all six distances fit perfectly on a plane, then the data are compatible with flat geometry.
If they do not, then the surface on which these distances were measured is not a plane.
And this is exactly where the problem appears—the strips cannot be assembled into a quadrilateral with both diagonals.
Over small areas, the Earth can be approximated as flat. That’s why a map of a single city or even a region works fine. But as distances grow large enough, the curvature of the surface begins to show.
On a sphere, geometry differs from planar geometry:
* angle sums differ,
* diagonals behave differently,
* distances between points no longer follow standard Euclidean rules.
Therefore, real-world distances between cities do not fit well into a flat model.
And this can be tested literally by hand, on an ordinary table—without satellites, NASA, or “faith in scientists.”
