Flat Earth? Let’s test the model
You do not have to begin with space photographs or someone else’s authority. Choose a map, route, or simple experiment and see which model produces consistent, repeatable results.
Interactive map · three calculators · scientific sources
Is Earth flat? No—but it is not a perfect sphere either.
The simplest useful model of Earth is a sphere. More precise measurements describe it as an oblate ellipsoid: slightly flattened at the poles and wider at the equator. Geodesy also uses the geoid, a surface connected to Earth’s gravity field and mean sea level.
That distinction matters. Saying “Earth is a sphere” is a good approximation in conversation and education, while GPS, surveying, and navigation use more precise models. None of those measurements requires a flat disc.
The strongest case does not rely on one photograph. Shadows, stars, eclipses, routes, the horizon, and daylight are independent observations, yet they lead to the same overall shape and a similar planetary radius.
The same planet. Two ways of looking.
Switch views, turn on distortion layers, and see what happens to the Southern Hemisphere on the disc map.
This north-pole-centred projection is often presented as the “flat Earth map”. It is actually a mathematical projection of a globe and strongly stretches the south.
Do not stop at the picture. Calculate the result.
Route test
Compare the shortest path on a sphere with a constant-bearing route.
- Great circle
- 11,347 km
- Rhumb line
- 12,784 km
- Difference
- 1,437 km
Shadow experiment
Enter the distance between measurements and the difference in shadow angle.
Distance to the horizon
Check the geometric horizon for a chosen observer height.
Six observations. One consistent model.
Each test concerns a different phenomenon. A good model must explain all of them with the same assumptions, rather than adding a separate correction for every case.
Shadows in different cities
Measure the Sun’s angle at several locations at the same time and the results change systematically with distance.
Spherical geometry turns those angles into Earth’s circumference. A third and further locations test both the Sun’s distance and the curvature of the surface.
Stars and latitude
The altitude of Polaris above the horizon is approximately equal to the observer’s latitude.
Travel south and Polaris drops, then disappears, while stars invisible in the north appear. A globe predicts this pattern without changing the sky model.
Earth’s shadow in a lunar eclipse
Earth’s shadow crossing the Moon is curved regardless of where the eclipse appears in the sky.
A sphere is the solid that casts a circular shadow from every direction. This observation predates spaceflight by many centuries.
The horizon and disappearing objects
A receding ship or building disappears from the bottom first. Raising the observer reveals part of it again.
Horizon distance grows predictably with height. Refraction can move the observed boundary, but it does not remove the global pattern.
Southern Hemisphere routes
Direct routes between Australia, Africa, and South America have travel times consistent with distances on a globe.
A north-pole-centred azimuthal map stretches the south more and more. It therefore cannot preserve the scale of all southern routes at once.
Day, night, and seasons
Half the planet is illuminated at one time, and the day–night boundary changes position during the year.
A rotating globe with a tilted axis predicts day length, polar night, and opposite seasons in both hemispheres with one geometric system.
Flat Earth — frequently asked questions
Earth is enormous relative to a person. At an eye height of about 1.7 m, the horizon is roughly 4.7 km away, so the visible arc is tiny. Wide-angle lenses and atmospheric refraction also affect how a photograph looks.
A calm water surface settles perpendicular to the local direction of gravity. It looks planar locally, but over large distances it follows Earth’s equipotential surface—the geoid.
We mainly sense acceleration, not constant velocity. Earth, the atmosphere, and the observer rotate together almost uniformly. The motion can still be measured with a Foucault pendulum, gyroscope, or the Coriolis effect.
No. Lines on a map depend on its projection, and connections also depend on airline networks and hubs. Direct flight times, especially in the south, agree with globe distances.
The UN emblem uses an azimuthal equidistant projection because it places all countries around a shared centre without favouring one meridian. It is a projection of a sphere onto a plane, not a statement about Earth’s shape.
No. Earth’s shape and size were measured long before photography through shadows, surveying, astronomy, meridian arcs, and eclipse observations. Modern satellites provide additional independent confirmation.
The result should be independently checkable.
The calculators use 6,371 km as the mean spherical radius. That is sufficient for educational experiments but does not replace a reference ellipsoid in precise geodesy. The horizon result excludes atmospheric refraction and terrain.