The horizon is only the start.
A sea that looks level, a world drawn as a disk and a shadow crossing the Moon. The shape of the whole has to account for all of them.
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A CLAIM ABOUT THE WORLD SHOULD FIT THE WHOLE WORLD.The water horizon sits 5,048 m away and an elevated target adds 11,288 m, giving 16.34 km of shared sightline. Set both heights and watch it move.
How far can these two heights see?
02A southern parallel of 7,076 km is drawn 23,580 km long on a north-polar disk, a 3.33× stretch. Move the latitude and watch the error grow with it.
Measure the same latitude arc on both maps
03A tilted disk throws an oval shadow 100 cm by 50 cm, an axis ratio of 0.5. A sphere casts a circle at every angle. Set the tilt and compare the edges.
How round is a tilted disk’s shadow?
The ocean looks level across the small patch visible from the shore.
Water finding its level requires a flat global surface.
Level is defined by gravity. Global mean sea level follows a curved, uneven surface called the geoid. A local horizontal describes the place where you stand, not a plane extending across the planet.
Read the full investigationA map can arrange the continents around a central point on a flat sheet.
A convincing disk map shows that the globe is unnecessary.
Projection preserves selected properties while distorting others. An equidistant map keeps particular distances, not every distance between every location. The paper’s shape is a mapping choice; the distortion reveals what that choice costs.
Read the full investigationDuring a partial lunar eclipse, a curved dark edge moves across the Moon.
A flat disk can explain Earth’s round eclipse shadow just as well.
A disk can cast a circle from one direction, but Earth’s shadow remains round across differing eclipse geometries. A spherical Earth explains that repeated shape as the planet blocks sunlight.
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